* Compound words: This is the most general term for words formed by combining two or more words. Examples include "sunlight" (sun + light), "highchair" (high + chair), and "notebook" (note + book).
* Blends: This refers to words that are formed by combining parts of two words, often the beginning of one word with the end of another. Examples include "smog" (smoke + fog), "brunch" (breakfast + lunch), and "motel" (motor + hotel).
* Portmanteau: This term is often used interchangeably with "blend" but sometimes specifically refers to a word formed by merging two words, often for humorous effect. Examples include "chortle" (chuckle + snort), "spork" (spoon + fork), and "shopaholic" (shop + alcoholic).
Ultimately, all of these terms describe the process of creating a new word by combining two existing words. The specific term you use depends on the specific method of combination and the context.