* "Plas-tic" with a long "a" sound has a long sound.
* "Plas-tik" with a short "a" sound has a short sound.
Both pronunciations are correct, but the first one is more common in American English.
* "Plas-tic" with a long "a" sound has a long sound.
* "Plas-tik" with a short "a" sound has a short sound.
Both pronunciations are correct, but the first one is more common in American English.