Не трогай сосульки: одна сосулька может упасть прямо на тротуар.

Don’t touch the icicles: one icicle can fall right onto the sidewalk.

Breakdown of Не трогай сосульки: одна сосулька может упасть прямо на тротуар.

• не: not
• мочь: to be able
• один: one
• прямо: right

Questions & Answers about Не трогай сосульки: одна сосулька может упасть прямо на тротуар.

Why is it не трогай, not не тронь?

Both are possible, but they feel a little different.

• не трогай uses the imperfective verb трогать
• не тронь uses the perfective verb тронуть

In warnings and general prohibitions, Russian very often prefers the imperfective imperative:

• Не кури. = Don’t smoke.
• Не открывай окно. = Don’t open the window.
• Не трогай сосульки. = Don’t touch the icicles.

So не трогай sounds like a normal, natural warning: don’t mess with / don’t touch them.

Не тронь is possible too, but it is often felt as sharper, more abrupt, or more like don’t touch it even once.

Why is трогай singular? Who is being addressed?

Трогай is the informal singular imperative form, used when speaking to:

• one person you address with ты
• often a child
• sometimes a general reader/listener in short warning language

Compare:

• Не трогай сосульки. = Don’t touch the icicles. (to one person / informal)
• Не трогайте сосульки. = Don’t touch the icicles. (to several people, or politely to one person)

So this sentence sounds like a direct warning to one person, perhaps a child.