GunnarKeiser, In "Bu küçük elmalar", "bu"-"this" is a demonstrative adjective, it modifies a specific thing, here "elmalar"="apples". "Bu" and "Bunlar"= "this"-"these" , when they are demonstrative pronoun, they are the subject of the verb 'to be" . "BU küçük elma"="THIS is a small apple" and "BUNLAR küçük elma" = "THESE are small apples". As Selcen say in her comment.
With no intended disrespect to dilara626239, I'm going to disagree with your first statement. It's a confusing topic, so I will include three sentences for comparison:
1) These are small apples = Bunlar küçük elma(lar)
2) These small apples = Bu küçük elmalar
3) These apples are small = "Bu elmalar küçük"
When "bu" is used as an adjective, it is always singular (whether it means "this" or "these"), as in: What kind of apples? ...These apples (ex. #2 and #3).
However, "bu" has multiple personalities, so it can also be a demonstrative pronoun. Ex. "Bu küçük bir elma" = "This is a small apple". In effect, we are saying: "This thing/ this fruit/ this drawing, etc.... is a small apple." So now "bu" is replacing a noun, rather than describing it. When it's used in this way, "bu" always means singular ("this"), and we're finally allowed to pluralize when necessary... and "bunlar" is born! Bunlar küçük = These are small; Bunlar küçük elma(lar) = These are small apples. (ex. #1)
As a sidenote: "Bu" sentences can sometimes be ambiguous (ex. “Bu su” = “This water” –OR – “This is water”), but "bunlar" is always a demonstrative pronoun.
And that's the long, scenic way around to answering Akash's question: "Why not These are small apples?" Hope it helps anyone who took the time to read it! :-)
Is the following true: If the adjective is after the noun like "bu elmalar küçük" then it means these apples are small or these are small apples, while if the adjective is before the noun like "bu küçük elmalar" then it means that these small apples!!! And i am confused about the difference between "bu küçük elmalar" and "bunlar küçük elmalar" why does the second mean these apples are small if the adjective is before the noun.
Bu kücük elma : these small apples Bu elmalar küçük : these apples are small Bunlar küçük elmalar : these are small apples</pre>
I put those tree sentences together and i notice in the two last ones that the suffix "lar" "introduce" the verb "are". It's difficult not to refer to french language. But if i have to translate a türkish text, i can't do otherwise, isn't it? If there is no verb "to be" in türkish, i can't stop myself anticipating and imagining there are suffixes to express the past: "apples were small this year"................
Bunlar can only be a demonstrative pronoun... NOT a demonstrative adjective. When we are using "this" or "these" as an adjective, Turkish will always use "bu".
- bu küçük elmalar = these small apples
- Bunlar küçük elma(lar). = These are small apples.
I made a post comparing "bu" and "bunlar" higher up on this page (in response to Akash_Polyglot). It's a bit long, but it might help you understand the difference. If it's still unclear, let me know and I'll do my best to help :-)