Alliteration occurs with what words in "Fire and Ice" by Robert Frost?

Alliteration is the repetition of the initial consonant sound in words which are adjacent or close together.  It can be used, especially, to affect the mood of a poem as well as to reinforce meaning.  In line 1, the words "Some say" and "world will" make use of alliteration on the s sound and the w sound, respectively.  The repetition of the words "Some say" in line two is also an example of anaphora(a...

Alliteration is the repetition of the initial consonant sound in words which are adjacent or close together.  It can be used, especially, to affect the mood of a poem as well as to reinforce meaning.  In line 1, the words "Some say" and "world will" make use of alliteration on the s sound and the w sound, respectively.  The repetition of the words "Some say" in line two is also an example of anaphora (a type of refrain where words are repeated at the beginnings of lines).  In line 4, the words "favor fire" use alliteration of the f sound.  Notice that many of the repeated sounds are quite soft, and this -- combined with the end rhyme -- makes the poem sound deceptively light and song-like.  This renders the final understatement, that "for destruction ice / Is also great / And would suffice," all the more jarring.  The subject matter of the poem seems to call for the repetition of more dramatic sounds; we are talking about the end of the world, after all.  But the lightness of the sounds and brightness of the end rhyme does not prepare us for the idea that ice (or hate) will merely "suffice" to end the world (in other words, the tone here is sort of off-handed or rather blase, as though hate would only just get it done). It's an understatement because hate would more than suffice; it is not a stretch to imagine that hatred could result in our destruction.

Indeed, there are other sound similarities in the poem.  For example, the s sound that is alliterative in "Some say" is also duplicated in "ice," though not at the beginning of the word.  Therefore, if we are to discuss the s sound including all three of these words -- some, say, and ice -- the sound similarity has a different name: it's called slant (or approximate) rhyme.  Slant or approximate rhyme refers to any kind of sound similarity in words that are close together; therefore, it is the most accurate way to refer to the s sound when it moves around (at the beginning of some words, the end of others, and so on).