Overview
All four locate one action within the span of another, but they frame that overlap differently. 最中に places you at the peak, smack in the middle of an ongoing action — often about to be interrupted. 途中で places you partway along a process or journey — “on the way,” at some midpoint. うちに frames a window of opportunity — “while the state still lasts / before it changes,” urging you to act before it’s too late. ついでに frames piggybacking — doing a second thing while you’re already at the first. The shorthand for students: 最中に = right in the middle (interruption), 途中で = along the way, うちに = while the window lasts, ついでに = tacking a second errand onto the first. The entries lead with a simple example, then a funny one, and draw the boundaries.
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