I have heard sentences like "He don't like this ." Or "He don't know this ."
Shouldn't it be "He doesn't like this." And "He doesn't know this."
Why with singular person we use "don't" and not "doesn't" ?
I have heard sentences like "He don't like this ." Or "He don't know this ."
Shouldn't it be "He doesn't like this." And "He doesn't know this."
Why with singular person we use "don't" and not "doesn't" ?
You are right, it should be "He doesn't like this." Sometimes people use it incorrectly on purpose or in an attempt to sound like a redneck. You'll also hear it used in African American Vernacular English (AAVE).
There are several possible reasons you might encounter this. These include:
1) The speaker/writer is a learner who does not know the correct way to conjugate the verb.
2) The speaker/writer speaks a dialect that doesn't emphasize correct conjugation.
3) The speaker/writer is trying to invoke a certain mood (this could be anything from rural mountain folk to urban people on the streets).
In short, the usage may be due to a lack of education, or it may be quite deliberate.
A recent ELL question asked something similar about a Bob Dylan lyric, and someone pointed out that Dylan has been awarded the Nobel Prize for Literature.