The noun 'warmth' is an uncountable noun, a word for a quality.
The noun 'warmth' is expressed by a partitive noun (also called a noun counter) a noun used to count or quantify an uncountable noun, for example 'great warmth' or 'a little warmth'.
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Yes, warmth is used as both a concrete noun and an abstract
noun. The noun warmth can be felt physically from a source of heat,
or warmth can be felt emotionally from a source of comfort or
kindness.