The opposite of an exit is an entrance. It is the area where you enter.
"I'll meet you at the entrance of the mall."
Exit（[出口](https://eikaiwa.dmm.com/uknow/questions/35032/)）の反対は、Entrance（入口）と言います。
例：I'll meet you at the entrance of the mall.（[モール](https://eikaiwa.dmm.com/uknow/questions/65225/)の入口で待ち合わせね。）
All of these answers are words to call an entrance to something, therefore the opposite of an exit.
A 'gateway' is an entrance that can be open and closed with a gate. The gate does not have to be any particular size to be described like this.
'Access in' or 'doorway' can be used in the same way. For example "I walked through the doorway into the restaurant" or "Here is the access into the hospital."
三例とも、何かの入口を表します。'exit'（出口）の反対です。
'gateway' は、ゲート（gate）を開け閉めする入り口を言います。ゲートの大きさに関係なく使えます。
'access in' や 'doorway' は同じように使うことが出来ます。
【例文】
"I walked through the doorway into the restaurant"
（入り口を通ってレストランに入った）
"Here is the access into the hospital."
（ここが病院の入り口です）
In order to explain places that allow you access to a desire place, you would say "Entrance" or "Way in". "Entrance" is the most commonly used and basic word to describe trying to access a place. Sometimes, "Way in" is used, the opposite of this would be "Way out" which is most commonly called an exit.
The most informal and common way of asking where the entrance is asking "How do I get in?" or "Where is the way in?". In this context, words such as, "access" and "doorway" are less commonly used and would be more often found in video games or movies.
入り口の場所を尋ねる最もインフォーマルで一般的な言い方は、
"How do I get in?"（どこから入ればいいですか）
または、
"Where is the way in?"（入り口はどこですか）
です。
この文脈では、"access" や "doorway" などの単語はあまり使われません、これらどちらかというとテレビゲームや映画で使われることが多いです。
The most common term that is used to describe where one can enter into a house, store, building, etc, is known as an entrance. Also used, less commonly, is "Entry Point." Even rarer, and usually used only in architecture and engineering, do we have an "Ingress/Egress point", the egress meaning that you can enter and exit through the same point.
If you are looking to go into a place (enter) then the most common term is 'entrance' which is the opposite to exit. This is sometimes called 'way in' as well
"exit"「出口」の反対の意味の「入口」は、"entrance"です。
また、レストランなどの「入口」は、
"front entrance door" / "front door"
と言ったりします。
"Let's sit at tables near the front door."
「入口の側に座ろう。」
ご参考になれば幸いです。
日本 
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イギリス 
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