Learn French: Nous avons perdu le neuvième match.

When making an ordinal number (a word like first, second, or ninth) from a number ending in -f, the f changes to a v before adding the -ième ending. So neuf becomes neuvième. This change makes the word flow much better when spoken.

Since Nous is plural, why doesn't perdu end with an -s?

Because this sentence uses the helping verb avoir (avons). In the passé composé, past participles only agree with the subject if the helping verb is être. With avoir, you only add an -s or -e if the direct object comes before the verb, which isn't the case here.

Why does neuvième go before match? I thought French adjectives usually go after the noun.

You are right that most descriptive adjectives go after the noun in French. However, ordinal numbers indicating position or order (like premier, deuxième, and neuvième) are exceptions to this rule and always come directly before the noun they modify.

Is match a masculine or feminine word here?

It is masculine, which is why the sentence uses le neuvième match. A helpful tip: when French borrows a word directly from English, like le match or le week-end, that word is almost always masculine.