Is the suffix -ion in the word invention the same as in the words direction, nation, fiction, station?
The -ion suffix is a suffix, appearing in words of Latin origin, denoting action or condition.
It is used in Latin and in English to form nouns from stems of Latin adjectives ( communion; union ), verbs ( legion; opinion ), and especially past participles ( allusion; creation; fusion; notion; torsion ).
(from latin directus - meaning to lay straight)
(from latin natio - meaning birth)
From Latin fictionem, accusative of fictio (“a making, fashioning, a feigning, a rhetorical or legal fiction”), from fingere (“to form, mold, shape, devise, feign”).
From Latin statiō, meaning station, stem sto meaning I stand.
So getting back to your question, the answer is that -ion serves the same purpose in all of those words from being latin stems into instances (or conditions) of that stem. It doesn't have a meaning in it's own right, but rather modifies the meaning of the stem.
Most importantly, many of the words that now end in -ion have evolved past this basic interpretation of how -ion modifies the stem. This means that for most words, the fact that they end in -ion is useful for etymological reasons or as a guideline, but that the words now have a meaning that is not any longer directly related to how the -ion suffix alters the stem of the word.
We can see this in the following:
directus (to lay straight) -> "direction" (literally "to lay straight") -> idiomatic evolution over time -> current meaning.
Similarly natio (birth) -> nation (place of birth) -> current meaning evolved over time
fictionem (to invent, to feign) -> fiction (an instance of making up) -> current meaning "made up" (relation to literature evolved over time).
sto (I stand) -> statio (I am standing/*I am stationed*) -> station (a place where one is standing) -> current meaning evolved over time.