on, onto, or on to?
Onto is usually preferable to on where movement is involved, as in I lifted the child onto [not on] my shoulders, and onto is always the better choice where on would be ambiguous: She jumped onto [not on] the platform. Unlike into, the preposition onto can be written as two separate words: He stepped onto [or on to] the sidewalk. Using onto, however, avoids the risk of confusion with the adverb on followed by the preposition to, which indicates progression and should not be joined together: We walked on to [not onto] the end of the road. Let us move on to [not onto] the next topic. See also into.
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