non-verbal spells

Spells performed without saying the incantations out loud.

References from the canon

• Silent spells are often used to do ordinary things such as closing curtains (HBP1, HBP19), moving furniture (PA9, HBP4), conjuring food (CS5), and lighting fires (PS4, GF5).
• Snape taught non-verbal spells as DADA teacher in Sixth Year (HBP9). As the year went on, silent spells were expected in both Transfiguration and Charms classes as well (HBP11). Hermione was the first in her class to repel a Jinx using a silent Shield Charm, but Harry forgot and shouted "Protego" (HBP9).
• The Patronus Charm can be done silently (HBP8)
• House-elf magic seems to be mostly wordless, such as Dobby's Hover Charm on Privet Drive (CS2).
• Hagrid started a fire wordlessly at Hut-On-Rock, then performed a Pigtail Jinx on Dudley without words (PS4)
• Quirrel silently sent a Hurling Hex that nearly bucked Harry from his broom during the first Quidditch match (PS11)
• Mr. Weasley performed a Mending Charm on Harry's glasses in Diagon Alley (CS4)
• Remus Lupin created fire as well as a Patronus Charm silently on the Hogwarts Express (PA5)
• Lupin lit candles without a verbal spell (PA12) and performed an Untransfiguration spell (with Sirius Black) on Peter Pettigrew in the Shrieking Shack (PA19)
• Dumbledore moved the furniture of the Great Hall out of the way and conjured squishy purple sleeping bags while silently waving his wand (PA9)
• Snape conjured ropes non-verbally to tie up Lupin, who later does the same for Wormtail (PA19) Ironically, Wormtail wordlessly tied Harry to a tombstone to take his blood so the Dark Lord could rise again (GF32).
• The Weasley Twins took turns making  Zacharias Smith's wand fly away with a silent Disarming Charm while practicing in the Room of Requirement with Dumbledore's Army (OP18).
• Kingsley Shacklebolt performed a nearly-silent Memory Modifying Charm on Marietta Edgecomb in the Headmaster's Office (OP27).
• The Death Eater Antonin Dolohov had a way with Dark non-verbal spells, nearly killing Hermione with wordless curse during the Battle of the Department of Mysteries (OP35). Madam Pomfrey said though the curse was "less effective than it would have been had he been able to say the incantation aloud" it still  "quite enough damage to be going on with" (OP38)
• The Headmaster wordlessly conjured a crystal goblet in the sea cave (HBP26), and later performed a silent Full Body Bind on Harry at the top of the Astronomy Tower (HBP27)
• Bellatrix Lestrange killed Sirius Black with a non-verbal spell that pushed him backwards through the Death Veil at the Department of Mysteries (OP35). She also killed a fox near Spinner's End with a non-verbal Killing Curse (HBP2).
• At the Battle of Hogwarts, Molly Weasley killed Bellatrix with a silent Avada Kedavra (DH36).