This is the 50th most frequent German word.
diese
"Diese" means "this" or "these" in English.
In this sentence, "diese" acts as a demonstrative determiner referring to a singular, feminine noun (Blume).
Diese Blume ist schön.
This flower is beautiful.
In this example, "diese" is used for plural nouns (Hunde) regardless of gender.
Diese Hunde laufen schnell.
These dogs run fast.
Here, "dieses" modifies a singular, neuter noun (Buch).