Rule 110.4 · Permanents
There are six permanent types: artifact, battle, creature, enchantment, land, and planeswalker. Instant and sorcery cards can’t enter the battlefield and thus can’t be permanents. Some kindred cards can enter the battlefield and some can’t, depending on their other card types. See section 3, “Card Types.”
Subrules
The term “permanent card” is used to refer to a card that could be put onto the battlefield. Specifically, it means an artifact, battle, creature, enchantment, land, or planeswalker card.
The term “permanent spell” is used to refer to a spell that will enter the battlefield as a permanent as part of its resolution. Specifically, it means an artifact, battle, creature, enchantment, or planeswalker spell.
If a permanent somehow loses all its permanent types, it remains on the battlefield. It’s still a permanent.