Tan and tanto are obviously related to each other, and they are both used in making what are known as comparisons of equality. However, they are not used the same way: Tan is used with adverbs and adjectives, while tanto (and its variations) is used with nouns.


Comments
Please correct me where I’m wrong.
‘Tanto’, often used as a modifier, is used as an adverb or as an adjective. It can also be used as a pronoun and as a noun (substantives) as in ‘tanto 1′ (futbol). And so forth … as mentioned in your article.
‘Tan’ is ‘Tanto’ apocopated and as such functions solely as an adverb modifying an adjective ( some comparative adjectives), adjective phrases and adverbial phrases, as well as other adverbs.
It appears to me then that while ‘tanto’ functions as more than one part of speech, in its apocopated form, is used only as an adverb.
Thanks.
That sounds like a good way of thinking about it. Tan is an apocopated forum whose use is less flexible than the full form.