Learn Turkish: İyi ki birikim yaptın. - Luckily, you saved money.

It is derived from the verb birikmek, which means "to accumulate" or "to gather". By adding the noun-forming suffix -im, we create the abstract noun birikim, which translates to "accumulation" or "savings".

Why does this sentence use yaptın (you did/made) instead of a specific verb for saving?

The noun birikim pairs with the auxiliary verb yapmak to form birikim yapmak (to build savings / to save money). Another very common way to express this is para biriktirmek (to accumulate money), but using birikim emphasizes the abstract concept of having savings.

Does birikim only refer to financial savings?

Not at all. Since it simply means "accumulation," it is widely used in other contexts. A great B2-level phrase to know is bilgi birikimi, which means "accumulation of knowledge" or "background knowledge."

Is it grammatically correct to write iyi ki as a single word?

No, it must always be written as two separate words. The ki here functions as an independent conjunction, unlike the suffix -ki (as in evdeki). Writing iyiki is a very common spelling mistake among native speakers, but it is officially incorrect.