Hi, Steve. I scheduled this appointment ‘cause it has been a while since we touched base.为什么要有个base？
Hi, Steve. I scheduled this appointment ‘cause it has been a while since we touched base.最后为什么要有个base？直接说Hi, Steve. I scheduled this appointment ‘cause it has been a while since we touched.不就行了吗？

Question

Answer

If you're asking which is correct, the first one means it has been a long time since you contacted each other and had a chance to exchange updated news/information.  "To touch base" is an idiom that means this.  Saying "... it has been a while since we touched" means that you want to physically touch the other person in a romantic or sexual way: by eliminating the "base," you are now using the literal meaning of the verb "to touch."

Answer

Since we touched不严谨啊，至少也应该是since we got in touch.

Evden çıkmadan dil öğrenme fırsatını kaçırmayın. Deneyimli dil eğitmenlerimizden oluşan seçkimize göz atın ve ilk dersinize şimdi kaydolun!