Learn Turkish: Bugün gri bir tişört giyiyorum. - Today I am wearing a grey t-shirt.

In Turkish, the word bir (a/an) usually goes between the adjective and the noun. You don't say "a grey t-shirt" (bir gri tişört), but rather "grey a t-shirt" (gri bir tişört). This is the standard rule anytime you use an adjective with a singular countable noun.

Is tişört just the English word "t-shirt"?

Yes! Turkish has borrowed many modern words from English and simply spells them exactly how they sound using the Turkish alphabet. The ş makes an English "sh" sound, making tişört sound almost identical to its English equivalent.

Does giyiyorum mean "I am putting on" or "I am wearing"?

It can actually mean both! The root verb giymek covers both the action of putting clothes on and the ongoing state of wearing them. Context usually tells you which one makes sense, and here "I am wearing" is the most natural translation.

How do you break down the verb giyiyorum?

It starts with the verb stem giy- (wear). We then add the present continuous tense suffix -iyor, which gives it the "am ...ing" meaning. Finally, we add -um, which is the personal ending for "I". Put it all together: giy-iyor-um.