The word "intension" can be a bit tricky because it sounds similar to another word, "extension," but they have different meanings. Here’s a simple explanation of "intension":
Intension (noun): It refers to the concept or the meaning of a word or expression that helps us understand what it refers to. It is what you need to know to understand the specific qualities or characteristics of something.
In more advanced discussions, "intension" is contrasted with "extension." While "intension" focuses on the qualities that define something, "extension" refers to the actual instances or examples of that thing (e.g., all the actual dogs in the world).
There aren't specific idioms or phrasal verbs that use "intension," but understanding phrases like "the meaning of" or "what it refers to" can be helpful when discussing related concepts.
To sum up, "intension" is about understanding the meaning and characteristics of a word or expression. It is an important concept in discussions about language and philosophy.