Learn Turkish: Onlar bugün denize gitmiyor. - They are not going to the sea today.

The -e is the dative case suffix, which means to or towards. Since the verb gitmek (to go) involves movement to a destination, we add this suffix to the destination noun. Following e-type vowel harmony, deniz takes -e, making denize (to the sea).

Earlier I learned that going is gidiyor. Why does the verb keep a t in gitmiyor?

The root of the verb is git-. Normally, when adding a suffix that starts with a vowel (like -iyor), the t softens to a d (making gidiyor). However, because the negative suffix in this sentence starts with a consonant (m), the t does not change.

Where does the negative meaning come from in gitmiyor?

The negative meaning comes from the -mi- right before the -yor suffix. The standard negative suffix for this verb is -me, but when the present continuous suffix -yor is attached, the e narrows to an i. This makes the word gitmiyor instead of gitmeyor.

Could I change the word order and say Bugün onlar denize gitmiyor?