You’ve probably heard of prefixes and suffixes, but these are just a part of the larger idea of morphology, which breaks words into their smallest meaningful parts.
Words can be seem difficult to spell, but by breaking them into meaningful parts, spelling is easier.
It also helps one gain a better understanding of unknown words by creating connections between parts.
Take 'subterranean'. It can be broken into 'Sub-', 'terra' and '-nean'.
Meaning 'under', 'ground' and 'relating to'.
From this, a rough definition of subterranean can be made, such as 'Relating to being underground'.
