Standard Swahili combines a few everyday fraction words with transparent numerical phrases. Nusu means “half,” robo means “quarter,” and sehemu “part” builds general fractions. Decimals use nukta “point,” while percentages begin with asilimia. The arithmetic is regular, but the grammar differs according to whether the number is counting parts, reading digits, or naming a proportion.
The crucial agreement principle remains the same as with whole numbers: numeral stems one through five agree when they modify a classed noun; six, seven, nine, and ten are invariable; eight also agrees. Digits read after nukta, however, identify places in a written number and use bare counting forms.
Nusu: half an amount or half of a whole
Nusu can stand before a measured unit or occur in nusu ya + noun phrase when a definite whole is being divided.
Ninahitaji nusu kilo ya unga wa mahindi na nusu lita ya maziwa.
I need half a kilo of maize flour and half a liter of milk.
Tulikula nusu ya mkate, kisha tukaihifadhi nusu iliyobaki.
We ate half of the loaf, then saved the remaining half.
Nusu kilo names a measurement. Nusu ya mkate selects half of a particular loaf. English uses “half a” and “half of”; Swahili makes the distinction with a bare measurement versus the associative form ya.
For mixed quantities, place na nusu after the whole amount:
Tumengoja kwa saa moja na nusu, lakini fundi bado hajafika.
We have waited for an hour and a half, but the technician still has not arrived.
This means 1½ hours. Nusu ya saa mbili instead means half of two hours—one hour—and is not the neutral way to say “two and a half hours.”
Robo: a quarter and clock quarters
Robo means one quarter. It appears in measurements, portions, and time expressions.
Ongeza robo kilo ya sukari, si nusu kilo, kwa sababu matunda tayari ni matamu.
Add a quarter kilo of sugar, not half a kilo, because the fruit is already sweet.
Tulipanga robo ya wanafunzi kufanya mazoezi asubuhi.
We scheduled a quarter of the students to practice in the morning.
For three quarters, robo tatu is common and transparent. Class 9/10 robo takes the bare-looking class-10 numeral tatu.
Tangi limejaa robo tatu, kwa hiyo bado kuna nafasi ya kuongeza maji.
The tank is three quarters full, so there is still room to add water.
In an East African clock expression, na robo means a quarter past and kasorobo a quarter to. The hour itself is still counted from about six o'clock.
Tutakutana saa tatu na robo asubuhi mbele ya benki.
We will meet at a quarter past nine in the morning in front of the bank.
The numerical hour saa tatu is 9:00 a.m.; adding na robo gives 9:15, not 3:15.
Sehemu: general and explicit fractions
Sehemu means “part/section.” It offers a transparent formal way to express a fraction as a number of equal parts. The clearest frame is:
sehemu + numerator + kati ya + denominator
| Fraction | Transparent phrase | Literal structure |
|---|---|---|
| 1/3 | sehemu moja kati ya tatu | one part among three |
| 2/3 | sehemu mbili kati ya tatu | two parts among three |
| 3/5 | sehemu tatu kati ya tano | three parts among five |
| 4/5 | sehemu nne kati ya tano | four parts among five |
The numerator modifies class 9/10 sehemu, so one through five appear in the class-9/10 shapes moja, mbili, tatu, nne, and tano. They do not take human wa- or class-8 vi-.
Sehemu mbili kati ya tatu za bustani zitatumika kupanda mboga.
Two thirds of the garden will be used to grow vegetables.
Tulimaliza sehemu tatu kati ya tano za kazi kabla umeme haujakatika.
We finished three fifths of the work before the electricity went out.
The plural head sehemu controls associative za. In mathematical, (academic), or technical writing, specialized fraction terms also occur, but the sehemu… kati ya… frame remains explicit and broadly understandable.
Nukta and decimal reading
Use nukta for the decimal point in speech. In careful reading, especially with measurements, money, or data, read each digit after nukta separately. This preserves place value and makes zeros audible.
| Written form | Read aloud |
|---|---|
| 0.5 | sifuri nukta tano |
| 2.04 | mbili nukta sifuri nne |
| 3.75 | tatu nukta saba tano |
| 10.08 | kumi nukta sifuri nane |
Kipimo kimeshuka kutoka tatu nukta saba tano hadi tatu nukta tano sifuri.
The reading has fallen from 3.75 to 3.50.
The final sifuri matters: 3.50 may carry a stated precision that 3.5 does not in a laboratory report. None of the post-nukta digits takes noun-class concord; they are names of digit values.
—Uzito halisi ni kilo ngapi? —Ni kilo mbili nukta sifuri nne.
—What is the exact weight? —It is 2.04 kilograms.
In (formal) technical speech, digit-by-digit reading is safer than grouping saba tano as “seventy-five.” Written institutions may follow different punctuation conventions for the visible separator, so always confirm the printed format in financial or scientific documents; the spoken word remains nukta for a point.
Asilimia: percentages
Asilimia precedes the number: asilimia tano “five percent,” asilimia ishirini “twenty percent.” To name the whole from which the share is taken, use asilimia + number + ya + noun phrase.
Tulitumia asilimia sitini ya bajeti kukarabati madarasa mawili.
We used sixty percent of the budget to renovate two classrooms.
Bei ya unga imepungua kwa asilimia tano tangu mwezi uliopita.
The price of flour has fallen by five percent since last month.
Benki inalipa riba ya asilimia nne kwa mwaka kwenye akaunti hiyo.
The bank pays annual interest of four percent on that account.
Asilimia behaves as a class-9/10 numerical head. With one through five, its numeral therefore has the class-9/10 surface form: asilimia moja, mbili, tatu, nne, tano. Six and seven remain bare, while class-9/10 eight is also surface nane.
Do not insert ya between asilimia and the number. The linker comes only before the whole: asilimia kumi ya mapato, not asilimia ya kumi mapato.
Fractions, decimals, and percentages in one calculation
The three systems can describe the same proportion but suit different contexts:
Nusu ya washiriki ni sawa na asilimia hamsini, yaani sifuri nukta tano ya kundi lote.
Half the participants equals fifty percent, that is, 0.5 of the whole group.
Nusu is most natural in everyday division, asilimia hamsini in reports and comparisons, and sifuri nukta tano in numerical or (academic) calculation. The expressions are mathematically equivalent, not grammatically interchangeable inside every noun phrase.
A practical arithmetic statement uses ordinary bare numbers:
Nusu jumlisha robo ni robo tatu.
One half plus one quarter is three quarters.
The fraction nouns frame the calculation; there is no need to make tatu agree with the object being divided unless a noun phrase actually supplies that controller.
Register and notation
Nusu and robo are ordinary in conversation, recipes, markets, and schedules. Sehemu… kati ya… is explicit and useful in teaching or (formal) explanation. Nukta and asilimia are standard in education, finance, science, news, and daily discussion of data.
For the low-numeral agreement underlying sehemu mbili and robo tatu, see agreement with numerals one through five.
Common Mistakes
Copying English “point” into decimal reading
❌ Bei imeongezeka kwa pointi mbili tano.
Incorrect decimal terminology — use nukta between the whole number and its digits.
✅ Bei imeongezeka kwa dola mbili nukta mbili tano kwa kila kilo.
The price has increased by 2.25 dollars per kilogram.
Putting ya between asilimia and its number
❌ Tulitumia asilimia ya tano ya akiba yetu.
Incorrect — the number follows asilimia directly.
✅ Tulitumia asilimia tano ya akiba yetu kununua mbegu.
We used five percent of our savings to buy seeds.
Giving sehemu human numeral concord
❌ Tumemaliza sehemu wawili kati ya watatu za ukaguzi.
Incorrect — sehemu is class 9/10, so the numerator is mbili, not human wawili.
✅ Tumemaliza sehemu mbili kati ya tatu za ukaguzi.
We have completed two thirds of the inspection.
Confusing half of an amount with an added half
❌ Safari ilichukua nusu ya saa mbili.
Incorrect if the intended duration is two and a half hours — this sentence means half of two hours.
✅ Safari ilichukua saa mbili na nusu kutoka bandarini hadi kijijini.
The journey took two and a half hours from the port to the village.
Key Takeaways
- Use nusu for a half and robo for a quarter; add them after a whole amount in moja na nusu or na robo.
- General fractions can be made explicit as sehemu mbili kati ya tatu.
- Read decimal digits individually after nukta, preserving any written zeros.
- Put the percentage number directly after asilimia and introduce the whole with ya.
- Agreement applies when a numeral modifies a classed fraction noun; identifying digits after nukta remain bare.
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Start learning Swahili →Related Topics
- Money, Prices and TransactionsA2 — Ask and state prices with shilingi, bei, costing verbs, place-value groups, and decimal currency subdivisions.
- Distributive and Approximate NumbersB1 — Group or distribute quantities with repeated numerals and kila, and estimate them with takriban or postposed hivi.