I saw a phrase saying “protruding eye”. Shouldn’t it be “protruded” ? I couldn’t understand why -ing is used instead of -ed and how the -ing form is used as an adjective here.
Many adjectives are ing, though there are also ones with ed or the irregular past participle. The meanings can change, too.
- protruding eye [like lizards, a regular type of eye for a lizard]
- protruded eye would be a regular eye that had damage done to it. A forensic analysis by have a term like that in it after a crime or accident.
- broken record [as in for music]; you sound like a broken record (repetitive); one that has been broken.
- breaking news: news that is emerging in the present time. Broken news is not a term.
- flying aces: pilots from WWI.
- flown routes: routes that have been flown by a pilot.
When the ing form is used, it is just a regular adjective. When the past participle is used, it often means something was done to the object.
- moving vehicles, vehicles in motion, that are moving
moved vehicles, vehicles that have been moved
floating beacons, ones that float
- floated beacons, ones that were put in the water and floated
You can often take the verb and analyze it as: an x that [verb] versus an x that has been [verb,past participle].
Often that helps to make the meaning clear.
protruding itself is an adjective and it means sticking out or projecting.
Therefore it is correct to say protruding eyes
Protrude is a verb.
Some verbs with the added suffix -ing act as adjectives. Protruding here is defining the characteristic of eyes.
Similar adjectives are "Interesting" ,"Exciting"
-ed is also used to turn verbs into adjectives. For example "Excited" and "Exciting" both are adjectives with different suffix