Early Primitive Elvish
taþa
root. count
noto Reconstructed
root. count
There are more words but they are from Tolkien's earlier conceptional periods. Tolkien likely changed these words as he evolved the aesthetics and completeness of the languages. You may even find languages that Tolkien later rejected. Do not mix words from different time periods unless you are familiar with the phonetic developments.
Below: Tolkien's Late Period (1950–1973). These are from Tolkien's late conceptual period — his most settled forms of the languages. Prefer these over the earlier ones above when composing new text.
The root {ᴱ√TASA >>} ᴱ√TAÞA “count” appeared in the Qenya Lexicon of the 1910s, with derivatives ᴱQ. tanta “number” and ᴱQ. tasta- “reckon” (QL/90). It also had derivatives in the contemporaneous Gnomish Lexicon such as G. {tant >>} tast “number” and {tath- >>} G. tathna- “number, count, reckon” (GL/69), the later the basis for {udathriol >>} G. udathnarol as in G. Nínin-Udathriol “[Battle of] Unnumbered Tears”, the earliest name for S. Nirnaeth Arnoediad of the same meaning. In Tolkien’s later writings, counting and number words were based on the root √NOT (Ety/NOT; PE17/62).