bana / bina

1. The forms.

• bat → bana
• bi → bina
• hiru → hiruna
• lau → launa
• bost → bosna (not bostna)
• sei → seina
• hamar → hamarna

In a longer number, only the last word changes: hogeita seina (twenty-six each), ehun eta seina (a hundred and six each). ehun becomes ehuna, but mila and milioi never take -na; add bana after them instead: mila bana (a thousand each), bosna mila (five thousand each). For very long numbers, speakers usually switch to bakoitza.

2. Word order. Follow the plain numbers from numbers and nouns: bana comes after the noun, like bat. bina can come before or after it (bina liburu or liburu bina), like bi. The rest come before it. There is no article: sagar bana, bina liburu, hiruna euro.

3. What it means. Each person in the group gets or has that amount:

• Ikasleek liburu bana dute. (The students have a book each.)
• Ikasleek liburu bat dute. (The students have one book, together.)

The same idea can be said with bakoitza: Ikasle bakoitzak liburu bat du. Use one or the other, not both: bakoitzak bana repeats the same idea.

The group must be plural, because each member gets a share: Guk liburu bana erosi dugu (We bought a book each), not Nik liburu bana erosi dut.

4. The verb. The verb agrees with the amount each person gets: sagar bana takes a singular verb (eman diegu), and bina liburu and higher numbers take a plural one (hartu dituzte, ordaindu ditugu).

5. Related words. erdi bana means half each. With -ka you get banaka (one by one) and binaka (in pairs).

Regional note: In the Northern tradition, numbers that end in a vowel often take -ra instead: bira (two each), seira (six each). The Academy accepts this use, but -na is the form taught everywhere: bina, seina.