Math in Esperanto: plus, minus, fractions and shapes

In Esperanto you read a sum by naming its signs: 2 + 3 = 5 is Du plus tri estas kvin. The signs are plus, minus, oble "times" and dividite per "divided by", and "equals" is estas, egalas or faras. Fractions use the suffix -on- (duono "half"), the decimal mark is a comma (komo), and shapes are nouns in -o: cirklo, kvadrato, kubo.

The number words themselves are on the numbers page. Pronunciation guides split words into syllables, with the stressed syllable in capitals.

#How do you read a sum aloud?

Name each sign, then the result. The Fundamento reads the equals sign with faras ("makes"): Du kaj du faras kvar. PMEG says estas and egalas (al) are more common today.

Oble attaches to the number before it (trioble, kvinoble) or stands alone (tri oble kvar). The Fundamento has Kvinoble sep estas tridek kvin, "five times seven is thirty-five".

Plus tri is a pozitiva nombro and minus tri a negativa nombro; zero is nul. For comparing, pli granda ol is "greater than" and malpli granda ol "less than": Kvin estas pli granda ol tri. For −10° PMEG gives minus dek gradoj or dek gradoj sub nulo. See comparison for pli and ol.

#What are the words for add, subtract, multiply and divide?

Each operation has a verb, and its outcome has its own noun. Outside technical talk, ReVo says aldoni "to add" and depreni "to take away" can replace adicii and subtrahi.

#How do you say fractions and percent?

A fraction is a number plus the suffix -on-, one of that many equal parts. Kvarono is an ordinary noun, so three of them are tri kvaronoj. See suffixes for -on-, -obl- and -op-.

As a prefix, duon- and kvaron- join the next word: duonhoro "half an hour", kvaronkilometro "a quarter of a kilometre". Multiples use -obl- and groups -op-: Dudek estas la duoblo de dek. The table adds groups and percent.

Say the number first, then the plural: dudek elcentoj or dudek procentoj for 20%. PMEG reads 100% as cent procentoj/elcentoj; ReVo marks pocento as one to avoid. La rabato estas dudek elcentoj. – "The discount is twenty percent."

#How do you say decimals and measurements?

Esperanto uses a decimal comma, not a point: 3,5 is tri komo kvin (PMEG). After the komo, read the digits one by one.

A digit after the comma is a decimalo. Units follow the number: kvadrata metro "square metre", kuba metro "cubic metre".

#What are the shapes called in Esperanto?

Flat shapes end in -o. ReVo defines kvadrato as a right-angled rhombus, a regular quadrilateral.

Solid shapes work the same way. The surface of a ball is a sfero; the object itself is a globo.

Kubo havas ses facojn, dek du eĝojn kaj ok verticojn. – "A cube has six faces, twelve edges and eight vertices." Kvadrato havas kvar egalajn laterojn. – "A square has four equal sides."

#Which words describe geometry and measurement?

A measurement takes the ending -n: La tablo estas du metrojn longa kaj unu metron larĝa. – "The table is two metres long and one metre wide." More examples:

• La sumo de la anguloj de triangulo estas cent okdek gradoj. – "The angles of a triangle add up to 180 degrees."
• Por kalkuli la areon de rektangulo, multipliku la longon per la larĝo. – "To find the area of a rectangle, multiply the length by the width."

#Nombro, numero or cifero: which one do you need?

Nombro is the quantity, numero is a number used as a label, and cifero is the written sign.

Ĉi tiu nombro havas kvar ciferojn. – "This number has four digits." Mi loĝas en ĉambro numero sep. – "I live in room number seven." PMEG separates the two: kvara means three came before, while numero kvar is just a label.

#Which words do you need in a maths lesson?

Mi ne povas solvi ĉi tiun ekvacion. – "I can't solve this equation." Ĉu mi rajtas uzi kalkulilon? – "May I use a calculator?" Kio estas la rezulto? – "What is the result?" The page on school and education has the rest of the classroom.

#How are these words built?

The parts never change, so many of these words can be read from their pieces: tri·angul·o "three-angle", kvar·later·o "four-side", plur·later·o "many-side", kalkul·il·o "calculate-tool". See word building, and use the number converter for fractions and multiples.

#Common questions

#How do you say plus, minus, times and divided by in Esperanto?

Plus, minus, oble (or multiplikite per) and dividite per. The equals sign is read estas, egalas al or, in the Fundamento, faras.

#How do you say 2 + 2 = 4 in Esperanto?

Du plus du estas kvar. The Fundamento's wording, Du kaj du faras kvar, is also correct.

#How do you say half, a third and a quarter in Esperanto?

Duono, triono and kvarono. Three quarters is tri kvaronoj, and percent is elcento or procento.

#How do you say 3.5 in Esperanto?

Write a decimal comma and say tri komo kvin, reading each digit after the komo separately.

#What is the difference between nombro, numero and cifero?

Nombro is a quantity, numero is a label such as a room number, and cifero is a written digit.

#How do you say circle, square, triangle and cube in Esperanto?

Cirklo, kvadrato, triangulo and kubo. A rectangle is rektangulo or ortangulo, and a sphere is sfero.

#Sources

• PMEG: Matematikaj esprimoj (reading sums, decimal comma, measures)
• PMEG: Plus kaj minus
• PMEG: O-vortaj nombrovortoj, Suffix ON, Suffix OBL, Suffix OP
• PMEG: Use of number words (numero), N for measure, Auxiliary signs (%)
• ReVo: plus, minus, egala, -obl-, oble, pozitiva, negativa, adicii, aldoni, depreni, subtrahi, multipliki, dividi, sumo, diferenco, produkto, kvociento, potenco, radiko
• ReVo: duono, triono, kvarono, centono, elcento, pocento, procento, rabato, komo, punkto, decimalo, decimala
• ReVo: cirklo, cirkla, kvadrato, kvadrata, rombo, paralelogramo, trapezo, pentagono, heksagono, plurlatero, kvarlatero, latero, angulo, triangulo, rektangulo, ortangulo, plurangulo
• ReVo: kubo, sfero, globo, piramido, cilindro, konuso, prismo, faco, eĝo
• ReVo: orta, orto, akuta, obtuza, rekta, rekto, streko, vertico, radiuso, diametro, cirkonferenco, perimetro, areo, volumeno, paralela, perpendikulara, longo, larĝo, alto, profundo
• ReVo: nombro, numero, cifero, kalkuli, kalkulilo, ekvacio, solvi, rezulto, matematiko, geometrio