Learn Hardcore German: Die zweite Brücke ist neu.

Many German nouns ending in -e are feminine (e.g. die Blume, die Straße, die Brücke). There are exceptions, so it’s best to learn the article together with each new noun.

Why does zweite end with -e?

Here zweite is an ordinal number (meaning “second”) used attributively before a feminine, nominative noun. In the weak declension of adjectives and ordinals, feminine nominative forms take an -e ending: die zweite Brücke.

What’s the difference between zwei and zweite?

zwei is the cardinal number “two.” zweite is the ordinal number “second.” If you want to say “the second bridge,” you must use the ordinal: die zweite Brücke.

How are ordinal numbers formed and declined in German?

For 1–19, add -te to the cardinal:
eins → erste, zwei → zweite, drei → dritte
From 20 upward, add -ste:
zwanzig → zwanzigste, dreißig → dreißigste
Decline them like adjectives:
Nom. die dritte Brücke, Akk. die dritte Brücke, Dat. der dritten Brücke, Gen. der dritten Brücke

Why isn’t neu inflected here (e.g. neue, neuer)?

Because neu is used as a predicate adjective after the copula sein (“to be”). Predicate adjectives in German remain uninflected:
Die zweite Brücke ist neu.

What’s the difference between die neue Brücke and die Brücke ist neu?

die neue Brücke: neue is an attributive adjective and must agree in gender, case, and number with Brücke (weak declension: -e).
die Brücke ist neu: neu is predicative (after ist) and therefore stays in its base form.

How would I turn this into a yes/no question?

Invert the verb and the subject:
Ist die zweite Brücke neu?

How do I ask “Which bridge is new?” in German?

Use the interrogative adjective welche, declined for feminine nominative:
Welche Brücke ist neu?