Which version of this phrase is correct and why is there a 是 at the beginning?

Question

In this sentence, the typical grammar structure for Subject + verb + place/object is not being used.

In the text, he says:

马克西：这是我的马克笔。是我在一棵树下找到的。

I am confused on the second sentence. I would write it as 我找到在一棵树下的 or 我在一棵树找到. (no 是 at the beginning).

What grammar structure does the native text use to say "I found it under a tree," and why does it make sense? Additionally, can someone ascertain whether my grammar rephrase is correct or not, and why?

Answer 1

这是我的马克笔。是我在一棵树下找到的。

This is a compound sentence - 复合句.

In which, "是" is a relative pronoun - "which" or "that", that connects a "main clause" and a "relative clause". For example:

"This is the table which I bought."

• This is the table = the main clause.
• I bought = the relative clause.
• which = the relative pronoun joining the two clauses.

For your example:

"这是我的马克笔。是我在一棵树下找到的。"

• This is my marker = the main clause.
• I found under the tree = the relative clause.
• witch (是) = the relative pronoun joining the two clauses.

Comment on your rephrases:

The first rephrase - "我找到在一棵树下的", is completely ungrammatical.

The 2nd rephrase - "我在一棵树(1)找到(2)"

• 1. You can't find a pen in a tree, a specific location relative to the tree needs to be specified - either "上", "下", "旁" or "附近".
• 2. At the end of a declarative or assertive sentence, you shall add "的" to ascertain the action you have stated.

Answer 2

马克西：这是我的马克笔。是我在一棵树下找到的。

是 doesn't start a sentence

是我在一棵树下找到的 is a dependent clause that adds information to the object "marker pen"

• The first thing about the marker is: "it is mine" (这是我的)

• The second thing about the marker is: "which I found under a tree" (是我在一棵树下找到的)

The correct sentence:

马克西：这是我的马克笔，是我在一棵树下找到的。 It is my marker that I found under a tree.

If you wrote "这是我在一棵树下找到的马克笔" (This is a marker I found under a tree), it doesn't say the pen is now yours