如何(いかん)Depending on

いかん is a grammar structure that has evolved as an abbreviation of 如何(いか)に, an adverb meaning 'in what way'. In almost all circumstances, it can be translated directly as 'depending on', and will be followed by either the auxiliary verb だ at the end of sentences, or the conjunctive form of だ, で, when used in the middle of a sentence.

いかん will follow nouns, and may or may not be preceded by の.

Occasionally, いかん will be followed by によって. This may seem like repetition for no particular reason, but in most cases it will just strengthen the original meaning of 'depending on', and can be literally translated as 'depending on what way (A) is oriented, (B)'.

いかん itself is used in a very similar way to 次第(しだい) 'upon (A)', or 'depending on (A)', and more often than not implies that the degree of (A) will be the factor that determines the overall result. Due to this, it will often be followed by subclauses that use verbs of decision making such as 決(き)まる.

Fun Fact

いかん, like いかに, is simply another word that has the same meaning as どう 'how', and even shares the same kanji structure of 如何(いかん), 如何(どう). It is also quite common to see the structure かどうであるによって 'depending on in what way' used as an explanation for the meaning of いかん in various dictionaries and other teaching resources. Due to this, it may be beneficial to simply consider いかん as a less common version of どう, or かどうである.