IPA: /ˈlɔːŋɡər/
KK: /lɔŋɡər/
This word describes something that has a greater length than something else.
The river is longer than the lake.
Longer → It is formed from "long" (from Old English "lang", meaning having a great distance or duration) and the comparative suffix "-er" (meaning more). The word "longer" means having a greater length or duration than something else.
Think of something that is 'more' ('-er') 'distant' or 'extended' ('long') — that's why longer means having more length.