However, in modern interpretations of English grammar, ordinal numerals are usually conflated with adjectives.
It is used in a variety of rankings, including time ('the first hour of the event'), space ('the first left'), and quality ('first class cabin').
The Latinate series 'primary', 'secondary', ... is often used for importance or precedence ('primary consideration') and sequence of dependence ('secondary effect', 'secondary boycott', 'secondary industry'), though there are other uses as well ('primary school', 'primary election').
[2] The first two in the sequence are by far the most common; 'tertiary' appears occasionally, and higher numbers are rare except in specialized contexts ('quaternary period').
The Greek series proto-, deutero-, trito-, ... is only found in prefixes, generally scholarly and technical coinages, e.g. protagonist, deuteragonist, tritagonist; protium, deuterium, tritium; Proto-Isaiah, Deutero-Isaiah.