Learning Swahili: a practical guide
This is a written companion to the free Swahili course on LanguagePath: what the language is like, how it sounds, the phrases you will use first, how the course is structured, and what to watch out for. Everything here comes from the same lessons you can practise interactively above.
What Swahili is like
Swahili is wonderfully regular and every word is pronounced as it is written. There are no gender articles; instead nouns come in "classes" whose prefix changes for singular and plural: mtoto (a/the child) → watoto (children). Verbs take a subject prefix instead of a separate pronoun: ni- = I, u- = you, a- = he/she. So nataka = I want, unataka = you want. Word order is subject–verb–object, and a single word often covers both "a" and "the". A warm tafadhali (please) and asante (thank you) go a long way.
Words you may already know
Pronunciation notes
Swahili is beautifully phonetic — every letter is said the way it is written. Master these few sounds and you can read any word aloud.
- a e i o u — pure vowels — "ah, eh, ee, oh, oo", never glided, as in asante = ah-SAHN-teh.
- ng' — nasal "ng" as in "singer" — no hard g, as in ng'ombe = ng-OHM-beh (cow).
- r — lightly rolled r, as in rafiki = rah-FEE-kee.
- mb / nd / nz — nasal + consonant together, no vowel in between, as in mbili = M-bee-lee · ndizi = N-dee-zee.
- sh — "sh" as in shoe, as in shilingi = shee-LEEN-gee.
- ch — "ch" as in church, as in chai = chai.
- ny — "ny" as in "canyon", as in nyama = NYAH-mah.
First phrases
The pocket phrases below are the ones learners reach for most often. Say each one out loud a few times before moving on.
| Swahili | Pronunciation | Meaning |
|---|---|---|
| Jambo | JAHM-boh | Hello |
| Habari! | hah-BAH-ree | Hello / how are things? |
| Karibu | kah-REE-boo | Welcome |
| Kwaheri | kwah-HEH-ree | Goodbye |
| Habari yako? | hah-BAH-ree YAH-koh | How are you? |
| Jina langu ni Alex | JEE-nah LAHN-goo nee | My name is... |
| Asante | ah-SAHN-teh | Thank you |
| Asante sana | ah-SAHN-teh SAH-nah | Thank you very much |
| Tafadhali | tah-fah-DHAH-lee | Please |
| Samahani | sah-mah-HAH-nee | Excuse me / sorry |
| Ndiyo | N-dee-yoh | Yes |
| Hapana | hah-PAH-nah | No |
| Moja | MOH-jah | 1 |
| Mbili | M-bee-lee | 2 |
| Tatu | TAH-too | 3 |
| Nne | nn-eh | 4 |
| Tano | TAH-noh | 5 |
| Kumi | KOO-mee | 10 |
| Maji | MAH-jee | water |
| Chai | chai | tea |
| Kahawa | kah-HAH-wah | coffee |
| Mkate | M-kah-teh | bread |
| Samaki | sah-MAH-kee | fish |
| ...wapi? | WAH-pee | where is...? |
| Kulia | koo-LEE-ah | to the right |
| Kushoto | koo-SHOH-toh | to the left |
| Moja kwa moja | MOH-jah kwah MOH-jah | straight ahead |
| Kituo | kee-TOO-oh | the station |
| Hii ni bei gani? | HEE-ee nee BAY-ee GAH-nee | how much is this? |
| Nataka | nah-TAH-kah | I want |
How the Swahili course is structured
The course has 16 short lessons that build on each other. Each one introduces a few new pieces and then asks you to construct sentences you have never seen, before revealing the answer:
- Greetings — jambo · habari · karibu · kwaheri
- Polite phrases — asante · tafadhali · samahani · sawa
- Numbers 1–10 — moja · mbili · tatu · kumi
- I want" — nataka — nataka · ningependa · ni-
- Food & drink — maji · kahawa · mkate · samaki
- Directions — wapi? · kulia · kushoto · moja kwa moja
- Questions & "do you have…?" — una? · kuna? · nini · wapi
- Family — familia · mama · baba · rafiki
- Time, days & weather — leo · kesho · jana · hali ya hewa
- Small talk & your name — jina langu ni Alex · jina lako nani?
- Emergency & health — msaada! · daktari · hospitali · sielewi
- Tying it together — nataka · ningependa · a capstone scene
- Airport & tickets — uwanja wa ndege · pasipoti · tiketi · ndege
- The taxi — teksi · kwenda · hoteli · simama
- The hotel — reservation · chumba · ufunguo · usiku
- Ask for help — sielewi · polepole · Kiingereza
Inside the lessons
Here is how a few of the lessons explain the language, with worked examples and the word-by-word breakdown the course uses.
Greetings
Key pieces: jambo · habari · karibu · kwaheri
Let's start with the word you'll hear (and use) most: jambo — hello. It works for both "hi" and a friendly opening. Say it out loud.
- jambo (JAHM-boh) — hello
- habari (hah-BAH-ree) — hello / how are things? Memory hook: ≈ Arabic khabar (news).
- karibu (kah-REE-boo) — welcome
- kwaheri (kwah-HEH-ree) — goodbye
To say “Hello!” in Swahili: Jambo! (JAHM-boh). Built from jambo = hello.
To greet someone properly, ask habari yako? — how are you? And reply nzuri, asante — fine, thanks.
- Habari yako? (hah-BAH-ree YAH-koh) — How are you?
- Nzuri, asante (N-zoo-ree, ah-SAHN-teh) — Fine, thanks
- Salama (sah-LAH-mah) — peaceful / fine
To say “Hello, how are you?” in Swahili: Jambo! Habari yako? (JAHM-boh, hah-BAH-ree YAH-koh). Built from jambo = hello; habari yako? = how are you?.
Polite phrases
Key pieces: asante · tafadhali · samahani · sawa
The magic words of courtesy: asante (thank you) and tafadhali (please).
- asante (ah-SAHN-teh) — thank you
- asante sana (ah-SAHN-teh SAH-nah) — thank you very much
- tafadhali (tah-fah-DHAH-lee) — please
- samahani (sah-mah-HAH-nee) — excuse me / sorry
To say “Thank you very much” in Swahili: Asante sana (ah-SAHN-teh SAH-nah). Built from asante = thanks; sana = very.
karibu doubles as "welcome" and "you're welcome", so it pops up everywhere.
To say “A coffee, please” in Swahili: Kahawa, tafadhali (kah-HAH-wah, tah-fah-DHAH-lee). Built from kahawa = coffee; tafadhali = please.
To say yes: ndiyo . No: hapana . And sawa = okay / alright.
- ndiyo (N-dee-yoh) — yes
- hapana (hah-PAH-nah) — no
- sawa (SAH-wah) — okay
To say “Thank you, okay” in Swahili: Asante, sawa (ah-SAHN-teh, SAH-wah). Built from asante = thanks; sawa = okay.
Numbers 1–10
Key pieces: moja · mbili · tatu · kumi
Numbers are the fastest win. Listen and repeat: moja, mbili, tatu .
- moja (MOH-jah) — 1
- mbili (M-bee-lee) — 2
- tatu (TAH-too) — 3
- nne (nn-eh) — 4
- tano (TAH-noh) — 5
- sita (SEE-tah) — 6
- saba (SAH-bah) — 7
- nane (NAH-neh) — 8
- tisa (TEE-sah) — 9
- kumi (KOO-mee) — 10
To say “Two coffees, please” in Swahili: Kahawa mbili, tafadhali (kah-HAH-wah M-bee-lee, tah-fah-DHAH-lee). Built from kahawa = coffee; mbili = two; tafadhali = please.
Notice the mb at the start of mbili — say both letters together with no vowel between them.
To say “I have five” in Swahili: Nina tano (NEE-nah TAH-noh). Built from nina = I have; tano = five.
To say “Five bananas” in Swahili: Ndizi tano (N-dee-zee TAH-noh). Built from ndizi = banana(s); tano = five.
I want" — nataka
Key pieces: nataka · ningependa · ni-
The key verb to order anything: nataka — I want. Use it to ask for whatever you need.
ningependa — I would like — is the more polite version, perfect in restaurants and shops.
To say “I want water” in Swahili: Nataka maji (nah-TAH-kah MAH-jee). Built from nataka = I want; maji = water.
To say “I'd like a coffee” in Swahili: Ningependa kahawa (nee-ngeh-PEN-dah kah-HAH-wah). Built from ningependa = I would like; kahawa = coffee.
Here the prefix ni- means "I". u- = you, a- = he/she. Combine: unataka = you want.
To say “I want bread” in Swahili: Nataka mkate (nah-TAH-kah M-kah-teh). Built from nataka = I want; mkate = bread.
Food & drink
Key pieces: maji · kahawa · mkate · samaki
Eating out? Key words: maji (water), chai (tea), mkate (bread).
- maji (MAH-jee) — water
- chai (chai) — tea Memory hook: ≈ English chai (tea).
- kahawa (kah-HAH-wah) — coffee Memory hook: ≈ Arabic qahwa (coffee).
- mkate (M-kah-teh) — bread
- nyama (NYAH-mah) — meat
- samaki (sah-MAH-kee) — fish
- wali (WAH-lee) — rice
To say “Tea and rice, please” in Swahili: Chai na wali, tafadhali (chai nah WAH-lee, tah-fah-DHAH-lee). Built from chai = tea; na = and; wali = rice; tafadhali = please.
To order, use nataka or more politely ningependa . na = and.
To say “I'd like fish” in Swahili: Ningependa samaki (nee-ngeh-PEN-dah sah-MAH-kee). Built from ningependa = I would like; samaki = fish.
Delicious is tamu sana . Say it to a cook and watch them smile.
To say “It's delicious!” in Swahili: Tamu sana! (TAH-moo SAH-nah). Built from tamu = tasty / sweet; sana = very.
Directions
Key pieces: wapi? · kulia · kushoto · moja kwa moja
The most useful question on the move: …wapi? — where is…? Pair it with a place.
- ...wapi? (WAH-pee) — where is...?
- kulia (koo-LEE-ah) — to the right
- kushoto (koo-SHOH-toh) — to the left
- moja kwa moja (MOH-jah kwah MOH-jah) — straight ahead
- kituo (kee-TOO-oh) — the station
- mji (M-jee) — town / city
To say “Where is the station?” in Swahili: Kituo kiko wapi? (kee-TOO-oh KEE-koh WAH-pee). Built from kituo = station; kiko wapi? = where is it?.
To say “Where is the bathroom?” in Swahili: Choo kiko wapi? (choh KEE-koh WAH-pee). Built from choo = toilet; kiko wapi? = where is it?.
kulia = to the right and kushoto = to the left. Straight ahead is moja kwa moja .
To say “Straight ahead” in Swahili: Moja kwa moja (MOH-jah kwah MOH-jah). Built from moja kwa moja = straight ahead.
Questions & "do you have…?"
Key pieces: una? · kuna? · nini · wapi
To ask someone if they have something: una…? (one person) or mna…? (a group).
To say “Do you have a table?” in Swahili: Una meza? (OO-nah MEH-zah). Built from una = do you have; meza = table.
kuna…? = is there…? Great for asking what's available.
To say “Is there wifi?” in Swahili: Kuna wifi? (KOO-nah WEE-fee). Built from kuna = is there; wifi = wifi. ≈ English wifi.
Other question words: nini (what), nani (who), lini (when), wapi (where).
- nini (NEE-nee) — what
- nani (NAH-nee) — who
- lini (LEE-nee) — when
- wapi (WAH-pee) — where
- kwa nini (kwah NEE-nee) — why
To say “What is this?” in Swahili: Hii ni nini? (HEE-ee nee NEE-nee). Built from hii = this; ni = is; nini = what.
To say “Do you have bread?” in Swahili: Una mkate? (OO-nah M-kah-teh). Built from una = do you have; mkate = bread.
Family
Key pieces: familia · mama · baba · rafiki
Family words: familia (family), mama (mother), baba (father).
- familia (fah-MEE-lee-ah) — family Memory hook: ≈ English family.
- mama (MAH-mah) — mother
- baba (BAH-bah) — father
- mtoto (M-toh-toh) — child
- rafiki (rah-FEE-kee) — friend Memory hook: ≈ Arabic rafiq (friend).
To say “I have a friend” in Swahili: Nina rafiki (NEE-nah rah-FEE-kee). Built from nina = I have; rafiki = friend.
nina = I have, from ni- (I). Use it to say what you've got.
To say “I have a family” in Swahili: Nina familia (NEE-nah fah-MEE-lee-ah). Built from nina = I have; familia = family.
To say “This is my mother” in Swahili: Mama yangu (MAH-mah YAHN-goo). Built from mama = mother; yangu = my.
Time, days & weather
Key pieces: leo · kesho · jana · hali ya hewa
Today is leo , tomorrow is kesho , yesterday is jana .
- leo (LEH-oh) — today
- kesho (KEH-shoh) — tomorrow
- jana (JAH-nah) — yesterday
- hali ya hewa (HAH-lee yah HEH-wah) — weather
- siku (SEE-koo) — day
To say “See you tomorrow” in Swahili: Tutaonana kesho (too-tah-oh-NAH-nah KEH-shoh). Built from tutaonana = we'll meet; kesho = tomorrow.
Ask about the weather: Hali ya hewa ikoje? — how is the weather?
To say “It's raining” in Swahili: Kuna mvua (KOO-nah M-voo-ah). Built from kuna = there is; mvua = rain.
Days of the week start with Juma : Jumatatu (Monday), Jumanne (Tuesday), and so on.
- Jumatatu (joo-mah-TAH-too) — Monday
- Jumanne (joo-MAHN-neh) — Tuesday
- Ijumaa (ee-JOO-mah) — Friday
- Jumapili (joo-mah-PEE-lee) — Sunday
Small talk & your name
Key pieces: jina langu ni Alex · jina lako nani?
Introduce yourself: Jina langu ni… = my name is…, then say your name.
To say “My name is Alex” in Swahili: Jina langu ni Alex (JEE-nah LAHN-goo nee Alex). Built from jina = name; langu = my; ni = is; Alex = your name.
To ask someone's name: Jina lako nani?
To say “What's your name?” in Swahili: Jina lako nani? (JEE-nah LAH-koh NAH-nee). Built from jina = name; lako = your; nani = who.
To say “Pleased to meet you” in Swahili: Ninafurahi kukutana (nee-nah-foo-RAH-hee koo-koo-TAH-nah). Built from ninafurahi = I'm pleased; kukutana = to meet you.
To say where you're from: Unatoka wapi? — you come from where? Reply Ninatoka… .
To say “I come from America” in Swahili: Ninatoka Marekani (nee-nah-TOH-kah mah-reh-KAH-nee). Built from ninatoka = I come from; Marekani = America.
Emergency & health
Key pieces: msaada! · daktari · hospitali · sielewi
The most important word if you need help: msaada! — help!
- msaada! (M-sah-AH-dah) — Help!
- daktari (dahk-TAH-ree) — the doctor Memory hook: ≈ English doctor.
- hospitali (hos-pee-TAH-lee) — the hospital Memory hook: ≈ English hospital.
- duka la dawa (DOO-kah lah DAH-wah) — the pharmacy
- Sielewi (see-eh-LEH-wee) — I don't understand
To say “Help!” in Swahili: Msaada! (M-sah-AH-dah). Built from msaada = help.
To say you are unwell: Ninaumwa (I'm sick). To say you need a doctor: Nahitaji daktari .
To say “I need a doctor” in Swahili: Nahitaji daktari (nah-hee-TAH-jee dahk-TAH-ree). Built from nahitaji = I need; daktari = doctor. ≈ English doctor.
To say “I'm sick” in Swahili: Ninaumwa (nee-nah-OOM-wah). Built from ninaumwa = I am sick.
To say “Where is the pharmacy?” in Swahili: Duka la dawa liko wapi? (DOO-kah lah DAH-wah LEE-koh WAH-pee). Built from duka la dawa = pharmacy; liko wapi? = where is it?.
Tying it together
Key pieces: nataka · ningependa · a capstone scene
Great — you've built a real toolbox. This capstone uses only words you've met. Build each line yourself before revealing.
To say “Hello, how are you?” in Swahili: Jambo! Habari yako? (JAHM-boh, hah-BAH-ree YAH-koh). Built from jambo = hello; habari yako? = how are you?.
To say “I'd like water, please” in Swahili: Ningependa maji, tafadhali (nee-ngeh-PEN-dah MAH-jee, tah-fah-DHAH-lee). Built from ningependa = I would like; maji = water; tafadhali = please.
To say “How much is it?” in Swahili: Bei ni ngapi? (BAY-ee nee NGAH-pee). Built from bei = price; ni = is; ngapi = how much.
To say “Where is the station?” in Swahili: Kituo kiko wapi? (kee-TOO-oh KEE-koh WAH-pee). Built from kituo = station; kiko wapi? = where is it?.
Airport & tickets
Key pieces: uwanja wa ndege · pasipoti · tiketi · ndege
You have landed. The building is the uwanja wa ndege . Your document is a pasipoti .
- uwanja wa ndege (oo-WAHN-jah wah N-deh-geh) — the airport
- pasipoti (pah-see-POH-tee) — the passport
- tiketi (tee-KEH-tee) — the ticket
- ndege (N-deh-geh) — the flight
- lango (LAHN-goh) — the gate
To say “Where is the airport?” in Swahili: Uwanja wa ndege uko wapi? (oo-WAHN-jah wah N-deh-geh OO-koh WAH-pee). Built from uwanja wa ndege = the airport; uko wapi? = where is it?.
To say “Here is my passport” in Swahili: Hapa pasipoti yangu (HAH-pah pah-see-POH-tee YAHN-goo). Built from hapa = here is; pasipoti yangu = my passport.
To say “A ticket, please” in Swahili: Tiketi, tafadhali (tee-KEH-tee, tah-fah-DHAH-lee). Built from tiketi = ticket; tafadhali = please.
To say “Where is the gate?” in Swahili: Lango liko wapi? (LAHN-goh LEE-koh WAH-pee). Built from lango = the gate; liko wapi? = where is it?.
The taxi
Key pieces: teksi · kwenda · hoteli · simama
The driver is waiting. teksi is the word you need. Tell them where to go with nataka kwenda .
- teksi (TEK-see) — the taxi
- dereva (deh-REH-vah) — the driver
- nataka kwenda (nah-TAH-kah KWEHN-dah) — I want to go
- simama hapa (see-MAH-mah HAH-pah) — stop here
To say “Taxi, please” in Swahili: Teksi, tafadhali (TEK-see, tah-fah-DHAH-lee). Built from teksi = taxi; tafadhali = please.
To say “I want to go to the hotel” in Swahili: Nataka kwenda hoteli (nah-TAH-kah KWEHN-dah hoh-TEH-lee). Built from nataka kwenda = I want to go; hoteli = hotel.
To say “Stop here, please” in Swahili: Simama hapa, tafadhali (see-MAH-mah HAH-pah, tah-fah-DHAH-lee). Built from simama hapa = stop here; tafadhali = please.
To say “How much is it?” in Swahili: Bei ni ngapi? (BAY-ee nee NGAH-pee). Built from bei = price; ni = is; ngapi = how much.
The hotel
Key pieces: reservation · chumba · ufunguo · usiku
At the desk: Nina reservation — I have a reservation.
- hoteli (hoh-TEH-lee) — the hotel
- reservation (reh-sehr-VAY-shohn) — the reservation
- chumba (CHOOM-bah) — the room
- ufunguo (oo-foon-GOO-oh) — the key
- usiku mmoja (oo-SEE-koo M-moh-jah) — one night
To say “I have a reservation” in Swahili: Nina reservation (NEE-nah reh-sehr-VAY-shohn). Built from nina = I have; reservation = a reservation.
To say “A room for one night, please” in Swahili: Chumba cha usiku mmoja, tafadhali (CHOOM-bah chah oo-SEE-koo M-moh-jah, tah-fah-DHAH-lee). Built from chumba = a room; usiku mmoja = one night; tafadhali = please.
To say “The key, please” in Swahili: Ufunguo, tafadhali (oo-foon-GOO-oh, tah-fah-DHAH-lee). Built from ufunguo = the key; tafadhali = please.
To say “Where is my room?” in Swahili: Chumba changu kiko wapi? (CHOOM-bah CHAHN-goo KEE-koh WAH-pee). Built from chumba changu = my room; kiko wapi? = where is it?.
Ask for help
Key pieces: sielewi · polepole · Kiingereza
When the language is too fast: Polepole, tafadhali — slower, please.
- polepole (poh-leh-POH-leh) — slower
- tena (TEH-nah) — again
- Kiingereza (kee-een-geh-REH-zah) — English
- unaweza kunisaidia? (oo-nah-WEH-zah koo-nee-sah-DEE-ah) — can you help?
To say “I don't understand” in Swahili: Sielewi (see-eh-LEH-wee). Built from sielewi = I don't understand.
To say “Slower, please” in Swahili: Polepole, tafadhali (poh-leh-POH-leh, tah-fah-DHAH-lee). Built from polepole = slower; tafadhali = please.
To say “Can you help me?” in Swahili: Unaweza kunisaidia? (oo-nah-WEH-zah koo-nee-sah-DEE-ah). Built from unaweza = can you; kunisaidia = help me.
To say “Do you speak English?” in Swahili: Unazungumza Kiingereza? (oo-nah-zoon-GOOM-zah kee-een-geh-REH-zah). Built from unazungumza = do you speak; Kiingereza = English.
Culture and etiquette
Karibu
Hospitality is central to the culture. Karibu ("welcome") is said warmly and often — you'll hear it constantly in shops and homes. It also means "you're welcome" after thanks.
A language of the road
Swahili is the lingua franca of East Africa — spoken across Kenya, Tanzania, Uganda, Rwanda and beyond. A friendly greeting in Swahili opens doors almost everywhere in the region.
Hakuna matata
Hakuna matata — "no worries" — captures the relaxed, upbeat spirit of the coast. Say it with a smile and a laugh; it's the go-easy motto of everyday life.
Matatu culture
Colourful matatus (shared minibuses) are how most people get around Kenyan cities. They often blast music, and a conductor calls the route. Choose your matatu wisely and agree the fare before you board.
Greetings matter
Greet before you ask anything — start with a warm "Habari?" or "Jambo!". Jumping straight to business without a greeting is seen as rude.
Many dialects, one language
Standard Swahili is taught in schools, but local varieties differ — Zanzibar's coastal dialect and Kenyan slang each add colour. Hear a word you don't know? Just ask "Hii ina maana gani?" (what does this mean?).
Example dialogues
At a café (duka)
You: Habari! Nipe kahawa, tafadhali. (hah-BAH-ree, NEE-peh kah-HAH-wah, tah-fah-DHAH-lee) — Hello! Give me a coffee, please.
Server: Karibu. Kahawa na nini? (kah-REE-boo, kah-HAH-wah nah NEE-nee) — Welcome. Coffee with what?
You: Kahawa na mkate, asante. (kah-HAH-wah nah M-kah-teh, ah-SAHN-teh) — Coffee and bread, thank you.
Server: Haya. Ni shilingi mia tano. (HAH-yah, nee shee-LEEN-gee MEE-ah TAH-noh) — OK. That's five hundred shillings.
You: Asante sana! (ah-SAHN-teh SAH-nah) — Thank you very much!
On the matatu
You: Samahani, matatu hii inaenda mjini? (sah-mah-HAH-nee, mah-TAH-too HEE-ee ee-nah-EHN-dah M-jee-nee) — Excuse me, does this matatu go to town?
Driver: Ndiyo, ingia. (N-dee-yoh, een-GEE-ah) — Yes, get in.
You: Nataka kwenda kituo. Nauli ngapi? (nah-TAH-kah KWEHN-dah kee-TOO-oh, nah-OO-lee NGAH-pee) — I want to go to the station. How much is the fare?
Driver: Shilingi mia mbili. (shee-LEEN-gee MEE-ah M-bee-lee) — Two hundred shillings.
You: Haya. Nifike kituo, tafadhali. (HAH-yah, nee-FEE-kah kee-TOO-oh, tah-fah-DHAH-lee) — OK. Take me to the station, please.
At a restaurant
Waiter: Karibu! Una nini leo? (kah-REE-boo, OO-nah NEE-nee LEH-oh) — Welcome! What will you have today?
You: Nataka samaki na wali. (nah-TAH-kah sah-MAH-kee nah WAH-lee) — I want fish and rice.
Waiter: Na kinywaji? (nah kee-nyah-WAH-jee) — And a drink?
You: Maji, tafadhali. (MAH-jee, tah-fah-DHAH-lee) — Water, please.
Waiter: Haya. Chakula kiko tayari hivi karibuni. (HAH-yah, chah-KOO-lah KEE-koh tah-YAH-ree HEE-vee kah-ree-BOO-nee) — OK. The food will be ready soon.
Written by the LanguagePath editorial team from our own course material. Pronunciation guides are approximate English respellings; tap any phrase in the app above to hear it. Native-speaker review of every course is ongoing — tell us if you spot an error.