Slow
Late
い adjective
This is a single kanji with an い on the end, meaning you know it's probably an adjective. What's the adjective form of slow? It's slow (or, if you're slow, you're probably late, too).
おそい
How slow are you? You are oh so slow (おそ).
私のパソコンはハードディスクの容量が無くなってきているので、動作がすごく遅いです。
My computer is very slow because it’s running out of hard drive space.