a是个词根, in the state or process of.
有人问老板能不能去参加学术会议，老板答"go ahead"，他的意思可能是"去个头。"
go ahead
1. used to tell sb they can do sth
2. do sth that was planned, esp in spite of a problem, e.g. I'll go ahead with the meeting anyway.
3. take place, e.g. Tests of anti-coronavirus drugs are to go ahead this year. 'coroner' means 'crown' in Old French.
有head的词很多: arrowhead, spearhead(spear:矛), pinhead, warhead(导弹的战斗部), letterhead(信头)
A newspaper's masthead is the part at the top of the front page where its name appears in big letters.
egghead: sb who is very intelligent, 聪明的脑袋不长毛，热闹的马路不长草.
hothead: sb who does things too quickly without thinking
behead: 斩首; deadhead: remove the dead or dying flowers from a plant
redhead: 红发的人; forehead: the area at the front of the head between the eyebrows and the hair
airhead bonehead knucklehead blockhead: 都是骂人笨。
copperhead: a poisonous yellow and brown North American snake; rattlesnake: 响尾蛇
fountainhead: the origin of sth =source，源头
Mr. Potato Head. FRIENDS第1集，How much Barry looks like Mr. Potato Head. Well, 1. 学医很累; 2. 他后来植发(plant)了。