Compound words are made when two or more words join (with or without a hyphen) to form a new word and subsequently, a new meaning.
E.g: The word black is an adjective and board is a noun, but if you join them together, they form a new word - blackboard.
There are three different types of compound words:
Hyphenated form and
1. Closed form: Two words are joined together to create a new meaning.
For example: firefly, softball, redhead, keyboard, makeup and notebook.
2. Hyphenated form: The words are joined together by a hyphen.
For example: daughter-in-law, over-the-counter, six-year-old.
3. Open form: The words are open but when read together, a new meaning is formed.
For example: post office, real estate, full moon, half sister.
Compound Nouns are formed by combining two nouns.
Compound Adjectives are a combination of the following parts of speeches:
The combination of Noun + Adjective
The combination of Noun+ Verb
In compound nouns, the stress usually falls on the first syllable.