Learn Turkish: İçinde kulvar olmayan havuzlarda yüzmeyeceğiz. - We will not swim in pools that do not have lanes in them.

In a regular sentence, you would say İçinde kulvar yok (There are no lanes in it). However, the words var and yok cannot take relative clause suffixes like -An. To turn an existential sentence into a modifying phrase (a pool that does not have lanes), Turkish replaces var with olan and yok with olmayan.

Break down the word İçinde. Why does it have the -in- buffer?

It literally means 'in its inside'. It comes from the spatial noun iç (inside). It takes the 3rd person singular possessive suffix -i (its) referring to the pool, followed by the buffer consonant -n-, and finally the locative case suffix -de (in/at).

The English translation says 'lanes' (plural), but the Turkish says kulvar (singular). Why isn't it kulvarlar?

In Turkish existential clauses, the item that exists or is absent is usually kept in the singular form if you are talking about a general category. Saying kulvar olmayan expresses the general lack of a lane perfectly, whereas English prefers the plural 'lanes' in this context.

There are two locative words in this sentence: içinde and havuzlarda. How do they interact?