Learn Turkish: Pazartesi toplantıya katılmadım. - I didn't attend the meeting on Monday.

It breaks down like this: katıl (attend) + ma (negative suffix) + dı (past tense) + m (I). In Turkish, the negative suffix always goes directly onto the verb root, right before the tense suffix.

Why is there an -ya at the end of toplantıya?

The verb katılmak (to attend or join) always requires the dative case suffix (-a or -e, meaning "to"). You are essentially saying "I didn't join to the meeting." Because toplantı (meeting) ends in a vowel, we add the buffer letter -y- before the -a.

If the English translation says "on Monday", why is there no suffix on Pazartesi?

Unlike English, Turkish doesn't use a preposition or suffix (like the locative -de or -da) for days of the week when stating when an event happened. You simply say the day: Pazartesi.

Could I say Pazartesi günü instead of just Pazartesi?

Yes! Both are perfectly natural. Adding günü (day of) is very common in Turkish, but using just the day name like in this sentence is also completely correct and often used in everyday conversation.