1.
one end, one side
One end or extremity of a physical object such as a rope, road, or line.
2.
a part, a glimpse, one aspect
A portion or fragment of something larger, often used to describe catching a glimpse of someone's character, ability, or a situation.
Usage: The two senses have different usage patterns.
Sense 1 (one end): Used for physical objects with two ends.
Sense 2 (a part/glimpse): Used with abstract nouns to mean "a part of" or "a glimpse of."
Note: Do not confuse with 一旦 (once, temporarily), which is an adverb with a completely different meaning.