Trekking Trousers.
Once again there is a wide range of lightweight quick drying trousers and pants. A great advantage also is they don’t weight much. I wear these trousers over thermal leggings when it is cold. Trousers that allow conversion to shorts add versatility. Lots to choose from. I like the Columbia range however you have plenty of choice. Click the lins below to check out styles, prices and importantly read the reviews.
Columbia convertible pants 
Boxers (Underpants) and knickers.
The wrong choice can lead to groin problems particularly in men. Strongly suggest to void cotton as it holds moisture. Ideally choose quick drying synthetic, wool or wool blends. My favourites are wool anatomica boxers from Icebreaker. They are quick drying, wick away moisture and odour resistant My wife wears quick dry synthetic knickers.
Lots to choose from so check out the links below.