Last, this, next week
kinou, kyou and ashita stretched to weeks: sen- is last, kon- is this, rai- is next. Plus the weekend that everyone asks about.
senshuu
last week
先週 せんしゅう
Last week, for recaps. Like kinou, it pairs with past tense, and the same sen- gives sengetsu.
senshuu wa isogashikatta.
Last week was busy.
先週は忙しかった。
senshuu wa isogashikatta desu.
Last week was busy.
先週は忙しかったです。
konshuu
this week
今週 こんしゅう
This week. It works like kyou, taking past or non-past tense, and the same kon- gives kongetsu and konban.
konshuu wa chotto isogashii n da.
I'm kind of busy this week.
今週はちょっと忙しいんだ。
konshuu wa chotto isogashii n desu.
I'm a bit busy this week.
今週はちょっと忙しいんです。
raishuu
next week
来週 らいしゅう
Next week, a scheduling staple. Like ashita, it pairs with non-past tense, and the same rai- gives raigetsu and rainen.
raishuu wa isogashii?
Are you busy next week?
来週は忙しい？
raishuu wa isogashii desu ka?
Are you busy next week?
来週は忙しいですか？
shuumatsu
weekend
週末 しゅうまつ
The weekend, mostly in small-talk questions. Non-past (nani suru?) asks about the coming weekend, past (nani shita?) about the one just gone, and -teru about habit: shuumatsu wa nani shiteru no? (what do you usually do at weekends?).
shuumatsu nani suru?
What are you doing this weekend?
週末何する？
shuumatsu wa nani shimasu ka?
What are you doing this weekend?
週末は何しますか？
To pin down which weekend, say konshuumatsu (今週末) or raishuumatsu (来週末), one word each. konshuu no shuumatsu also works.