Usage of "onto"

Question

Sometimes I get confused about when to use on and onto.

Like in the following sentence:

And no matter how hard she tried to hold onto them, she would never be able keep them with her.

Should it be on or onto?

Answer 1

Onto and on to are distinct terms.

• Onto (one word) is a expanded form of on. It has fundamentally the same meaning, with in some cases a little more emphatic sense of directionality or force:

  The ship was driven onto the rocks ≈ The ship was driven on the rocks.

  It it is most usefully employed where bare on creates an ambiguity:

  He rode his motorcyle on the ferry might mean he rode his motorcycle while he was on the ferry, so instead we say
  He rode his bicycle onto the ferry.

• In your example, however, what is wanted is on to. This is two distinct words, and it is required because what is being used is the phrasal verb hold on, meaning approximately grasp:

  Hold on tight! means "Take a firm grip!".

  But unlike hold or grasp, hold on is intransitive: it does not take a direct object. The object grasped is instead designated with a prepositional phrase headed by to:

  Hold on to the railing means Grasp the railing.

The terms may be distinguished by pronunciation:

onto - /'ɔ^~tə/ (ɔ^~ is as close as I can get to nasalized /ɔ/) with a wholly reduced vowel at the end
on to - /'ɔntʊ/, with an only partially reduced vowel at the end.

But in rapid speech, unstressed on to often takes the onto pronunciation.

Answer 2

If your native language is German, it may be helpful to understand on as a dative preposition and onto as an accusative one. In any case, "I jumped onto the grass" has an entirely different meaning from "I jumped on the grass". The first means that I jumped from some place other than the grass to the grass, and the second means that I stood on the grass, jumped into the air (same idea with into versus in, by the way), and landed on the grass again.