This is the 5242nd most frequent Japanese word.
食後
"食後" means "after a meal."
Here, 食後 means 'after meals,' used generally to describe the time following eating.
食後は、散歩をするのが健康に良いです。
After meals, taking a walk is good for health.
In this sentence, 食後 specifies the timing for medication, indicating 'after meals' as a precise time.
医者は食後に薬を飲むように指示しました。
The doctor instructed to take medicine after meals.
The phrase 食後の indicates possession, referring to 'the act after meals,' specifying tooth brushing in this case.