What are combined words called? [duplicate]

Is there a grammatical rule to compound a set of words such as a single one? e.g. word1 word2 --> word1word2 or word1-word2? Bye.

Solution 1:

Here is a rule I read related to evolution of compound words.

Most compound words start out as two words :

Air plane, Space ship

Stage two, they are hyphenated :

Air-plane, Space-ship

Stage three, over time they start become accepted as a single word:

Airplane,Spaceship

I am not whether this answers your question, but hope it helps.