therefor / therefore are similar-sounding terms with different meanings (referred to as homophones). To better understand the differences, see below for definitions, pronunciation guides, and example sentences using each term. 👇
therefor: (adverb) (in formal usage, especially legal usage) for that or for it.
therefore: (adverb) (used to introduce a logical conclusion) from that fact or reason or as a result.
therefor: NA
therefore: dh·EH·r·f·AO·r
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)