Questions & Answers about Мне нужна пара носков.
Why is the word for socks written as носков here?
It is in the Genitive plural case because it follows a quantity word, пара (a pair). Just like in English we say 'a pair of socks', Russian uses the Genitive case to show what the pair consists of.
How exactly do we form the Genitive plural носков from the dictionary form?
The dictionary form is носок (a sock). Because it is a masculine noun ending in a hard consonant, it takes the -ов ending in the Genitive plural. Notice that the last о in носок is a fleeting vowel that drops out when endings are added. So the stem becomes носк-, and adding -ов gives us носков.
Why is the feminine form нужна used here instead of the default нужно?
In Russian 'need' constructions, the thing you need acts as the grammatical subject. The short adjective for 'needed' (нужен, нужна, нужно, or нужны) must match the subject's gender and number. Here, the grammatical subject is пара (a pair), which is a feminine noun, so we use the feminine нужна.
I know мне means 'to me', but why are we using it instead of я?