* Compound nouns are formed by combining two or more words to create a single new word. They can be written as one word (e.g., "toothbrush"), two words (e.g., "safety pin"), or hyphenated (e.g., "high-school").
* "Safety devices" is a noun phrase, meaning it's a group of words functioning as a noun. The words "safety" and "devices" are separate words that work together to describe the noun.
Examples of compound nouns:
* Fire escape
* Airbag
* Life vest
Examples of noun phrases:
* Safety procedures
* Emergency exits
* First aid kits