と言(い)うのは~ Known as ~ is, ~ Called ~ is, ~ Means ~, Because

というのは and ということは are similar in that both take a phrase and turn it into a topic for further explanation. While sometimes interchangeable, というのは is typically followed by a definition or reason. ということは is primarily used to rephrase, clarify, or draw a conclusion from the previous statement.

いわゆる and という both express the idea of something being 'called' something, but they are used very differently. いわゆる precedes a noun to mean 'the so-called (A)'. というのは takes a word or phrase and introduces it as a topic to be defined or explained. Because they serve different roles, they can be used together, e.g. いわゆる五月病というのは ('This thing known as the so-called May blues is...')

ことなの and というのは can both be used in explanations, but differ in position and role. ことなの appears at the end of a sentence to emphasize a conclusion or explanation. Literally, 'it's that it's (A)'. というのは follows a noun or phrase to introduce it as a topic to be explained. They can be used together, e.g. 人生というのはこういうことなんだ ('This thing we call life... this is what it means.')

ということ and というのは both turn phrases into nouns. ということ is often used to clarify what was said, while というのは introduces a topic for further explanation or comment. というのは can also start a sentence to mean 'what I mean is (A)' or 'that is to say (A)'.

Both expressions contain the same という, but are used differently. という is used to name or describe something, typically in the form AというB ('a B called A'). In contrast, というのは introduces something as a topic for explanation or comment, e.g. 人生というのは ('This thing we call life') While という is followed by a single noun, というのは is followed by a phrase that elaborates on the topic.