My dictionary sometimes lists two imperfective forms

Question

Consider the verb to send, which my dictionary translates as *посылать (imp.), слать (imp.), послать (perf.). My question is about those cases in which there are two imperfective forms, like in this one. Is there a general rule about the difference, if there are two?

Answer 1

This is quite a common case:

• слать - посла́ть - посыла́ть
• есть - съесть - съеда́ть
• жечь - сжечь - сжига́ть, etc

The prefixed imperfective verb normally denotes a periodic action while the unprefixed verb describes a continuous action:

• Он ка́ждую неде́лю посыла́ет ей пода́рок. - He sends her a gift every week.

• Он постоя́нно шлёт ей пода́рки. - He sends her gifts all the time.

• Он всё вре́мя ест. - He eats all the time / He can't stop eating.

• Он съеда́ет таре́лку ка́ши ка́ждый день. - He eats one plate of porridge every day.