Summoning Charm
Incantation: Accio
Pronunciation: ak-ee-oh
Description: This charm summons an object to the caster, potentially over a significant distance.
Seen: Harry summons his broom to complete the First Task of the Triwizard Tournament. Harry uses it to summon the Triwizard Cup after he encounters Voldemort.

Age Line Spell
Incantation: Unknown
Description: Creates a thin, shimmering line that can only be passed by people of a set age. Aging potions are useless against age lines.
Seen: In GoF, when Fred and George Weasley attempt to use an aging potion and step over the line, it appears to work, but moments later they are seen pulling off the Gandalf look better than Dumbledore himself.

Aguamenti
Pronunciation: ah-gwə-men-tee
Description: Produces a jet of water from the caster's wand.
Seen: Harry is taught how to perform this charm in Professor Flitwick's class in HBP and casts this spell in an attempt to create water for Dumbledore to drink after taking Voldemort's potion later that year.

Alohomora
Incantation: Alohomora
Pronunciation: ə-loh-hə-mohr-ə
Description: Used to open and/or unlock doors (doors can be bewitched so that this spell has no effect).
Seen: Used throughout the series, with the first use by Hermione in Harry Potter and the Philosopher's Stone.

Anapneo
Incantation: Anapneo
Pronunciation: ə-nap-nee-oh
Description: Clears the target's airway, if blocked.
Seen: In HBP, Horace Slughorn casts this spell on Marcus Belby when the latter begins to choke.

Anti-Cheating Spell
Incantation: Unknown.
Description: Cast on parchment or quills to prevent the writer from cheating whilst writing answers.
Seen: Cast on quills and exam papers for exams at Hogwarts.

Anti-Disapparition Jinx
Incantation: Unknown
Description: Used to prevent Disapparition and/or Apparition in an area for a period. Presumably can be used to prevent an enemy from entering a defended area, or used to trap an enemy in an area.
Seen: Used by Dumbledore to trap several Death Eaters in the Department of Mysteries. And at Hogwarts, "No one can Apparate or Disapparate inside the Hogwarts grounds."

Aparecium
Incantation: Aparecium
Pronunciation: ap-ə-ree-see-əm
Description: This spell makes invisible ink appear.
Seen: First seen in Harry Potter and the Chamber of Secrets, when Hermione tries to make hidden writing appear in Tom Marvolo Riddle's diary.

Killing Curse
Incantation: Avada Kedavra
Pronunciation: ə-vah-də kə-dah-vrə
Description: Causes instant, painless death to whomever the curse hits. There is no countercurse or method of blocking this spell. One of the three Unforgivable Curses.
Only two people in the history of the magical world are known to have survived the killing curse
Harry Potter who was hit twice directly, and Voldemort who had several horcruxes at the time.
Phoenixes can also survive a killing curse. They burst into flame as they would do in old age and are reborn from the ashes. This occurred in Harry Potter and the Order of the Phoenix.

Avis
Incantation: Avis
Pronunciation: ay-vis
Description: This charm creates a flock of birds from the caster's wand. When coupled with Oppugno, it can be used offensively.
Seen: In HBP, when Hermione attacked Ron cuz he was being an oblivious asshole.