1. Fresh chicken may be sold
in Hong Kong.
2. Fresh chicken may be disappeared
in Hong Kong. Ungrammatical
The word 'sold' is an adjective, so it takes a linking verb "be". But the word 'disappeared' is a verb, so it doesn't need another verb, like "be". Adjectives, not verbs, need a linking verb.
1. may (modal) be
(linking verb) sold
2. may (modal) disappear
(main verb, potential in meaning)
In short, "may be disappeared" is ungrammatical because there are two main verbs, 'be' and 'disappeared'. Either delete 'be' and -ed
(3) or change 'disappeared' to an adjective by replacing -ed
3. Fresh chickens may disappear
in Hong Kong.
4. Fresh chickens may be disappearing
in Hong Kong.
(A) Continuous Participle used as an adjective:
1. Before a noun: He is a tiring person.
2. Used on its own without aux: The team, tiring fast, lost the game.
3. Used with verb other than a form of Be: The journey seems tiring.
4. Used with a form of Be but not expressing a tense (i.e. preceded by a preposition): This is tiring TO me.
(B) Continuous Participle used as a verb:
1. Active voice, Present/Past Continuous tense: He is/was tiring fast.
1a. Active voice, Present/Past Perfect Continuous tense: He has/had been tiring fast.
2. Passive voice: Not applicable because passive voice always uses the Perfect Participle.
3. Active voice (with modal), Continuous tense: He may/might be tiring fast.
3a. Active voice (with modal), Perfect Continuous tense: He may/might have been tiring fast. ("Have" here is always the Infinitive, like "Been" here and in (1a) above is always the Perfect Participle).
4. Passive voice (with modal): Not applicable per (2) above.
(C) Perfect Participle used as an adjective:
1. Before a noun: This is a sold deal.
2. Used on it own without aux: The house, sold for a song, was worth a lot more.
3. Used with a verb other than a form of Have: The idea is sold on them. The idea seems sold on them.
4. Used with a form of Have but not expressing a tense: Not applicable.
(D) Perfect Participle used as a verb:
1. Active voice, Present/Past Perfect tense: They have/had sold the house.
2. Passive voice, Present/Past Perfect tense: The house has/had been sold.
3. Active voice (with modal), Perfect tense: They may/might have sold the house.
4. Passive voice (with modal), Perfect tense: The house may/might have been sold.
(E) Simple Present/Past Tense:
1. Active voice: He sells/sold the house(s).
2. Passive voice: The house(s) is/are/was/were sold.
3. Active voice (with modal): He may/might sell the house(s).
4. Passive voice (with modal): The house(s) may/might be sold.
(F) "Fresh chickens may be sold in Hong Kong" is (E) (4), and sold here is a verb, not an adjective.
(G) "He is gone from here" is (C) (3), and gone here is an adjective. The grammar point is that:
1. The PERFECT PARTICIPLE is never used to express a tense in the active voice with whatever form of Be.
2. The PASSIVE VOICE (with or without modal) can only be used with a transitive verb (a verb with a direct object, because we need the object in the active voice to become the grammatical subject in the passive voice). ["Gone" is intransitive.]
3. "Gone" as used in "He is gone" is not expressing a tense per (1), nor can it be in the passive voice per (2), so it is an adjective.
4. "Sold" as used in "Fresh chickens may be sold in Hong Kong" is expressed in the passive voice, with the active voice object "fresh chickens" (say, "People may sell fresh chickens in Hong Kong") being the passive voice grammatical subject.
I may be wrong, but I think I'm not.
If I may add:
The confusion arises because of (C)(3), (E)(2) and (E)(4).
1. (E)(2): The house is sold for $100k (verb). The house is sold already (adjective).
2. (E)(4): The house may be sold for $100k (verb). The house may be sold already (adjective).
3. Whether verb or adjective depends on the context.
(a) If in the given context, the Perfect Participle is DESCRIBING the grammatical subject of a sentence, then it is an adjective, and the sentence is NOT in the passive voice because the Perfect Participle is not used as a verb for construction of the passive voice.
(b) Where in the given context, the particple is expressing an action done TO the subject (passive voice), then it's a verb.
4. The context of the "chicken" sentence makes "sold" clearly a verb expressing the passive voice, not an adjective. It is clear that the sentence is NOT saying that the chickens may be (have been) already sold (off) in Hong Kong.
5. If we substitute "can" for "may", we see this even clearer: Fresh chickens can be sold in Hong Kong. 8)