Phrasal verbs are part of a large group of verbs called “multi-part” or "multi-word” verbs.
The preposition or adverb that follows the verb is sometimes called a particle.
Phrasal verbs and other multi-word verbs are an important part of the English language.
However, they are mainly used in spoken English and informal texts. They should be
avoided in academic writing where it is preferable to use a formal verb such as “to postpone”
rather than “to put off”.