For passive MP recovery, see Channeling.
Channeling spells are a group of spells that can be recast ("channeled") on subsequent turns by waiting (with . or s). They include:
Being moved by any effect (an elephant's trampling attack, the Primal Wave spell, an unintentional blink, etc.) ends the channel, as does Silence. Paralysis, confusion, sleep, and full petrification will pause channeling.
Searing Ray and Flame Wave cost the normal amount of MP for their initial cast, then 1 additional MP for every turn channeled. Searing Ray can be channeled up to three times, and Flame Wave, two (or three with Vehumet's range increase). Channeling does not decrease damage or any other statistic of the spell.
Maxwell's Capacitive Coupling instead uses channeling as a timer; after 3-7 turns waiting, it'll activate and instantly kill the closest enemy. It doesn't use any MP past the initial cast.
The amulet of the acrobat works with all channeled spells, as you are considered waiting (even if you are dealing damage).