Tree/Trees (Дерево/Деревья)

Is there a rule that results in the plural of "Дерево" being "Деревья"? Or is it just one of those quirks that you need to memorise?

There’s no rule. The plural number of nouns ending with “-jа” is the old collective form, which is archaic in it’s direct usage. Now, the old collective plural ending functions mainly as simple plural (i. e. opposed to singular). You can find exceptions also. I would recommend to make a list of this non-standrad plural and just learn it.

For example,

Singular --> Regular Plural --> Collective Plural
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гроздь (bunch) --> грозди (clusters) --> гроздья (bunches)
дерево (tree) --> N/A --> деревья (trees)
зуб (tooth) --> зубы (teeth) --> зубья (teeth = cogs)
кол (stake) --> колы (bad marks at school) --> колья (stakes)
колос (ear of a plant) --> N/A --> колосья (ears of plants)
корень (root) --> корни (roots) --> коренья (edible roots)
лист (leaf) --> листы (sheets) --> листья (leaves)
сын (son) --> сыны (sons, high flown style) --> сыновья (sons)

Very helpful! It did occur to me that it might have something to with collective nouns.

Thanks again.

Quote:

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Originally Posted by Rtyom

old collective form

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Thank you for explaining but I still don't get it..
what's 'old collective form'?

Just think of this:
Why do we say a herd of elephants but a flock of birds? we have special words for collectives. Old Russian (for ex. fifteenth century) had lots of things that are odd nowadays, and some leftovers still can be found in modern Russian. Why is the genitive singular used after numerals 2,3,4 but gen. plural after other numbers, aren't 2,3,4 plurals? These are things left over from a formerly much more complex Russian language.

Спасибо большое! :bravo: