根
ね · ne · JLPT N3 · noun
root
🌱🌳 木 tree + 艮 stay put = the part of a tree that stays put: its root
The left side 木 is tree; the right side 艮 carries the idea of stopping or holding firm. A root is what holds a tree in place. For the sound ね (ne), think of the word nest: roots nest deep in the soil.
根 — tree radical 木 + 艮 (phonetic)
根 is a semantic-phonetic compound. The left side 木 ('tree') gives the meaning, since the character originally referred to the roots of a tree. The right side 艮 supplies the sound. From 'tree root' it extended to mean 'root, base, foundation' in general.