Learn Turkish: Bu un taze. - This flour is fresh.

In Turkish, there isn't a standalone word for "is" in simple present tense sentences like this. The "to be" verb is usually invisible for the third person (he/she/it). So, Bu un taze literally translates to "This flour fresh," and the "is" is naturally understood.

The word un looks exactly like a suffix we've seen before. Is it related?

No, here un is a root noun meaning "flour." You might be thinking of the genitive case suffix (like the -un in onun, meaning "his/hers/its"), which happens to look identical but is just a grammatical ending. Remember to pronounce the noun un like the "oon" in "moon"!

How do we know Bu un means "This flour" instead of "This is flour"?

The word order tells us! Because taze (fresh) is at the end of the sentence, it acts as the main predicate (the part giving new information), so Bu un naturally groups together as the subject "This flour." If you wanted to say "This is fresh flour," the order would change to Bu taze un.