Breakdown of Дети делают игрушку, им нужен клей.
делать
to do
им
to them
игрушка
toy
нужен
needed (нужен, нужна, нужны)
Questions & Answers about Дети делают игрушку, им нужен клей.
Why does the sentence use нужен instead of нужны, since "children" is plural?
The word нужен (needed/necessary) is a short adjective that agrees with the thing that is needed, not the person who needs it. Here, the thing they need is клей (glue), which is a masculine noun. Therefore, we use the masculine singular form нужен.
Why is the word for "they" translated as им instead of они?
In Russian, expressing need with нужен requires the person who needs the item to be in the dative case. The sentence is structured literally as "To them, glue is necessary." Им is the dative form of они (they).
Why does игрушка change to игрушку in the first half of the sentence?
The children are making a toy, making "toy" the direct object of the verb делают (are making). Direct objects take the accusative case, which changes the feminine singular ending -а to -у.
How do we know the gender of клей to match it with нужен?
Клей ends in the letter -й (short i). Nouns ending in -й are always masculine in Russian, which is why it pairs with the masculine form нужен.