"Lunchtime" is the correct term for "中午" in English.
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The word "noon" can be used to refer to the middle of the day or 12:00 PM. However, if you specifically want to express the time in English, you can say "12:00 noon" or simply "midday."
"Midday" is a term commonly used to describe the time when the sun is at its highest point in the sky. It is generally understood to be around 12:00 PM, but can vary depending on the location and time of year.
In casual conversation, you can also refer to "noon" as "lunchtime" or "lunch hour," as it is the hour when many people take their midday break to eat.