In languages like English, the indefinite article is distinct from the numeral "one."  

<br><br><b>Reference</b><br>
Dryer, Matthew S.. 2008. Indefinite Articles.
In Haspelmath et al (2008), chapter 38.
Available online at <a href="http://wals.info/feature/38">
http://wals.info/feature/38</a href>.

