Learn Turkish: Sen annenle tenis oynayabilirsin. - You can play tennis with your mother.

It uses the ability suffix -ebil / -abil, which means 'can' or 'to be able to'. We start with the verb root oyna (play), add a buffer y because it ends in a vowel, then add -abil. Next is -ir for the present tense, and finally the personal ending -sin for 'you'.

Why is there an 'n' and an 'le' at the end of annenle?

The root word is anne (mother). The first -n is the possessive suffix making it annen (your mother). The -le is the shortened form of ile, which means 'with'. Put together, annenle means 'with your mother'.

If oynayabilirsin already means 'you can play', do we need to include Sen at the beginning?

Grammatically, no. Because the -sin ending on the verb already tells us 'you' are the one playing, the word Sen is optional. Including it here just adds a little extra emphasis to the sentence.

Why does the ability suffix use an 'a' (-abil) instead of an 'e' (-ebil) here?

This is due to vowel harmony. The last vowel in the verb root oyna is 'a', which is a back vowel. So, the suffix must follow suit and take the -abil form instead of -ebil.