# Why is “da” used in this question?

The following sentence comes from Duolingo:

Kiom da gekuzoj vi havas?

translates to:

How many cousins do you have?

da means of. Why is it used in this question? Is the question grammatically correct without it? It is not like I have a list of cousins (listo da gekuzoj).

• This is an example of the genitive case. en.wikipedia.org/wiki/Genitive_case. – jigglypuff Sep 16 '16 at 1:53
• shouldn't "how much of cousins" be 'how many...'? – Joe May 9 '17 at 7:43
• No, it is not, at least not in the core sence "possession" of the genetive. da is a quantitative expression. – Cyril Robert Brosch May 9 '17 at 7:59
• "Kiom da" means how much/many or what quantity – Lumo5 May 16 '17 at 14:47

Da and de both mean "of". Da is strictly used for quantities and measures. De is for possession and other uses.

Without the use of da here, there would be no relation between kiom and gekuzoj.

da
Prep. uzata por rilatigi du vortojn aŭ sintagmojn, el kiuj la unua esprimas mezuron (kvanton, pezon, longon, volumenon k.a.) de la dua
Preposition used to relate two words - the first expresses a measurement (quantity, weight, length, volume) of the second.

Examples:

• Sixty pages of text.
60 paĝoj da teksto
• One kilogram of tea.
unu kilogramo da teo
• A lot of paper.
multe da papero

Kiom is used without da in questions such as Kiom estas la duoblo de 6?, or Kiom estas la tempo?. It can be translated as "how much" followed by a numerical expression (algebraic, or of time): "How much is the double of 6?", "How much is the time" (not very elegant translation!)

Cousins are not a numerical expressions, so you add da to turn it into one: "How much of cousins do you have?" So kiom da is required to make sense, as it means "How much of".

(Examples from RosxReVo iOS app)

• duolo is new to me – Anton Sherwood Sep 15 '16 at 16:37
• @AntonSherwood That's because it's a typo! :) – Oliver Mason Sep 15 '16 at 16:54
• Bedaùrinde! Mi kredis havi okazon lerni novaĵon! – Anton Sherwood Sep 15 '16 at 20:14