Verb (5-dan, る, intransitive)
1. to be sufficient; to be enough
だがそれを説明するのには、時間が足らん。But there is not enough time to explain that.
2. to be worth doing; to be worthy of; to deserve
in the form に足る after a verb
この少年は信頼するに足る。This boy is worthy of trust.
3. to do (the job); to serve; to answer