1) Methyl 2) Methyl group 3) Methyl radical 1) Methylol 
Hydroxymethyl in the field of chemistry, particularly in organic chemistry, is the name for a substituent with the structural formula -CH2-OH. The hydroxymethyl group consists of a methylene bridge (-CH2- unit) connected to a hydroxy (-OH) group. This makes the hydroxymethyl group an alcohol. The hydroxymethyl group has the identical chemical form...
[n] - a methyl with hydroxide replacing the hydrogen atoms
hydroxymethyl A methyl with hydroxide replacing the hydrogen atoms.