prefix or suffix -en or en- ? a rule for them?

[prefix or suffix]

prefix or suffix -en or en- ? a rule for them?

we say strengthen but enlarge and enlighten? is tehre a certain rule for that ?
Thank Yo in advance

Kadir ALKAYA

[Tdol]

There's no single rule. The prefix has a meaning similar to 'give/provide' and the suffix, in this case, indicates that an adjective or, less commonly, noun has become a verb. 'Sadden' means to make sad, but 'endanger' means to place in danger, which is slightly different- it doesn't necessarily mean to make the danger.