-lich and -lig are endings that create an adjective, that has the vague sense of “like [word]”. There is no real difference between the two, and which one is used depends on what Germans have decided sounds best. Or actually, we should say “looks best”. Because it actually depends a lot on region and in the north for instance, people pronounce the -ig also as -ich.
Anyway, let’s look at some examples
- die Angst – ängstlich (scared, anxious)
- das Öl – ölig (oily)
- die Gefahr – gefährlich (“like danger”, dangerous)
- grün – grünlich (greenish)
The endings are primarily added to nouns, but they also works for some adjectives, and even some verbs. Then, the sense is more like the English -able.
- lesen – leserlich (legible)
- verstehen – verständlich (understandable)
- schläfrig – sleepy
Can we use them to make up new words?
Well, it can work for nouns at times, but more often than not, it’ll sound weird. And I wouldn’t recommend trying it for adjectives or verbs.
By the way… you might have already guessed it – the endings -lich and -lig are also the word like.
The origin of them all is the Germanic word *lik-, which meant something like body, shape, form and the idea of like and the endings was originally “of that form.“