This is the 5049th most frequent Arabic word.
المشي
Walking.
Here, the word 'المشي' functions as a gerund to signify the activity of walking as a general action.
أنا أستمتع بالمشي في الصباح.
I enjoy walking in the morning.
Here, 'المشي' is part of a noun phrase ('المشي السريع') describing a particular style of walking.
كان المشي السريع هو الأسلوب الذي استخدمه للوصول في الوقت.
Brisk walking was the method I used to arrive on time.
In this context, 'المشي' is used as an object noun representing the specific recommended activity.