silent /p/

[celtaflorida]

Greetings.
I'd like to know if there is rule for consonant /p/ to be silent as in psoriasis, or psychology. Does it have anything to do with the letter /s/? I would appreciate an explanation.
Thanks.

[SoothingDave]

Since English is your native language, it shouldn't be such a big problem for you.

[celtaflorida]

Thanks, but you failed to explain the grammatical rules.

[5jj]

There are no rules. Most of the words that begin with 'ps' come from Greek, and originally began with the Greek letter psi. This was pronounced roughly like /ps/, an unacceptable combination at the beginning of words in English; so, the /p/ disappeared.

[Tdol]

It's also usually silent in Phnom Penh for the same reason- it's hard to say, though this comes from a different language.

[birdeen's call]

It's silent in "Ptolemy" too, for similar reasons.

[raindoctor]

In a way, yes, it has to do with /s/. For instance, clusters like /pl/, /pr/ and /pw/ are permitted. So, p + any approximant other than /j/ is permitted.

[5jj]

For instance, clusters like /pl/, /pr/ and /pw/ are permitted. So, p + any approximant other than /j/ is permitted.

/p/ can be followed by /j/ - pew, pewter, dispute, etc. I can't at the moment think of any /pw/ combinations in English