A 1st level spell fits into a slot of any size, but a 9th level spell fits only a 9th level slot. Page 201, Dungeon & Dragons Players Handbook 5th edition. One class whose spell slots don't work ...

Casters in D&D use spells that require spell slots or cantrips for magic ... Here are some helpful Dungeons & Dragons 5e spells that any magic-using player should make use of during their adventures.

While some subclasses will provide non-magical classes with spells, the people who select the Bard, Cleric, Druid, Paladin ... to the 2024 version of D&D 5e, as it now heals 2d8 damage ...