What is the difference between "出勤" and "通勤"?

Question

As the title implies, I want to know the difference between "出勤" and "通勤".

Both of them mean "commuting to work" in English.

And which should I choose in the following sentence:

朝夕の（ａ．出勤　ｂ．通勤）ラッシュ時は電車が満員になる。

Answer 1

There is a fairly big difference in meaning between the two words.

[出勤]{しゅっきん} means "arriving at one's workplace". The focus is on your presence at work by a certain time and/or on certain days. It has an antonym [欠勤]{けっきん} = "absence" from work.

[通勤]{つうきん} means "commuting to and from work" and the focus is on the transportation method, the time it takes you to commute, how easy/tiring it is, etc. 通勤 has no antonym.

Thus, the answer for the question at the end should be 通勤. The word「[朝夕]{あさゆう}」 should give a clue as 出勤 cannot take place both in the morning and in the evening.

Answer 2

According to http://eow.alc.co.jp/search?q=%E5%87%BA%E5%8B%A4&ref=sa, 出勤 means "attending work" (like 出席)

通勤 means to commute to/from work. 通 here having the meaning of 通う（かよう)

thus the correction answer is b.