〜上（で）

検討(けんとう)した上(うえ)で、ご返事(へんじ)いたします。

Kentō shita ue de, gohenji itashimasu.

I will reply after considering it.

On a past form it means after doing, marking that step as necessary groundwork

仕事(しごと)をする上(うえ)で、信頼(しんらい)が一番(いちばん)大切(たいせつ)です。

Shigoto o suru ue de, shinrai ga ichiban taisetsu desu.

In doing this work, trust matters most.

On a dictionary form it means in the course of, stating what holds in that domain

二(ふた)つの意味(いみ)は接続(せつぞく)で見分(みわ)けます。

Futatsu no imi wa setsuzoku de miwakemasu.

The two senses are told apart by what precedes.

A past form is sequence in time; a dictionary form is a domain