Because when we're talking about a specific object, the plural form is used.
His white dog = Hans hvide hund. ("hvide" is the plural of "hvid"/"hvidt")
The white dog = Den hvide hund.
However, if we were to generally talk about a white dog, we would use the singular form:
- A white dog = En hvid hund.
Lesson 3 from Danish in 3 months (£3 second hand from Amazon!) The basic form of a Danish adjective (as you will find in a dictionary) is used unchanged in connection with nouns of common gender, singular, in their 'indefinite' form ('a') En sød kage: A sweet cake. En god kvinde: A good woman.
When adjectives are used to describe a singular neuter noun they usually require the addition of a t: Et sødt smil: A sweet smile. Et godt hjerte: A good heart.
In the indefinite form most adjectives end with an e: søde sager: sweet things. gode gerninger: good deeds
When an adjective is placed before a noun in the 'definite' form ('the'), the definite ending is not added to the noun. Instead, the adjective is preceded by another word, meaning 'the', which is the same word for 'it' and 'they': den for common gender singular, det for neuter singular and de for plural. The ending on the adjective is the same for all three: e.
Den søde smerte: The sweet pain. Det store måltid: The large meal. De dejlige oplevelser: The lovely experiences.
If you want to say 'the red one, the big ones' you simply use the appropriate form of den, det or de followed by the adjective ending in e: Den røde, de store
'grønne jordbæret' is not a valid sentence as it would roughly translate to 'green/s the strawberry/ies'.
When we talk about a specific object that has an attribute (the green strawberry),
the en/et (jordbæret) part at the end of the object is replaced by Den/Det/De at the beginning of the sentence.
- The child = Barnet.
- The red child = Det røde barn.
- The potato = Kartoflen.
- The yellow potato = Den gule kartofel.
- The shoes = Skoene
- The black shoes = De sorte sko.
Hope that helps ;-)
They sound very similar, but to my ear 'det' sounds more like "deh" whereas 'de' is like "dee." Also, think about which one is actually plausible to use in the sentence. Correct me if I'm wrong, but "De grønne jordbær" doesn't really make sense. I've mostly only seen 'de' used as "they", even though it appears to also have an alternate translation of "the".