An email's subject box is where a short summary of the email contents is typed. This allows the receiver of the email to decide on the possible contents and the importance of the email. Emails with blank subject boxes are more likely to be deleted unread.
Always put subject heading so that the person receiving the email can quickly see what the email is about.
The subject in the sentence "The box is very big" is "The box."
it is the box where you input your purpose
The purpose of a Combo Box is so that a person gets more food or whatever comes in the combo box, for less of a price then if they bought everything separate.
the purpose of a quick change gear box (as the name suggests) is to allow you to change gear quickly.
Subject occasion audience purpose (style)
The purpose of an HDMI splitter box is usually to connect multiple high-definition devices to an HDTV. The purpose of an HDMI splitter box is usually to connect multiple high-definition devices to an purpose of an HDMI splitter box is usually to connect multiple high-definition devices to an HDTV?
The purpose of the box wrench is to have a flat of the wrench on each flat of the nut, thus giving more turning effort. - I always use box wrenches on old, rusted or stubborn nuts.
its to reduce noise
The subject pronoun it will take the place of the subject noun phrase 'the lid of the box': It was left wide open.
box
Yes, the subject is the noun in the sentence.Example: The tissue box was out of tissues.