led

In the Standard stress system, it's accented as lēd, and whenever an ending is attached to it, the vowel e shortens (e.g. na ledu).

The derived relational adjective is leden icy, made of ice.

From this noun, there's a verb pair meaning freeze:

zaleđivati (zaleđuje) ~ zalediti («) freeze

It can be used when someone freezes something (e.g. you put meat in a freezer), but whan something freezes (either caused by someone, or just by cold), a se² must be used:

jezero se zaledilo the lake froze

A similar verb pair is:

smrzavati («) ~ smrznuti (smrzne) freeze

This verb pair can be used when you're not really turning into ice, but just feeling really cold (don't forget se² when it happens to the subject):

smrzavam se I'm freezing