How to say I lost my schoolbag in English

How to say I lost my backpack in English is introduced as follows:

I lost my backpack.

backpack: UK/?b?kp?k/? US/?b?kp?k/.

n.

Backpack (used by climbers, walkers or when carrying children), box-shaped backpack (with a light metal frame).

vi.

Backpacking.

Plural: backpacks.

Derivatives: backpacker n.

Bilingual examples:

Why?should?she?wait?to?backpack?across?Europe?with?you?

Why is she waiting to go backpacking in Europe with you?

For?instance,?a?goal?can?be?to?backpack?through?South?America?for?three?months?on?a$?1,000?per?month?budget,? or?to?live?in?an?eco-village?in?India?for?several?months.?

For example, $1,000 per month in travel funds can cover three months of backpacking in South America , or you can stay in an eco-village in India for a few months.

Backpacks?spread?the?load?over?a?wider?area.?

New backpacks spread the load over a larger area.

The?traditional?backpack?with?a?difference?─?it's?waterproof.?

This is different from the traditional backpack - it is waterproof.

These?backpacks?are?designed?to?carry?a?heavy?load.?

These backpacks are designed for carrying heavy objects.

He?lay?back?on?the?grass?using?his?backpack?as?a?pillow.?

He lay on his back on the grass using his backpack as a pillow.

He?staggered?a?little?under?the?weight?of?his?backpack.?

The backpack on him made him stagger a little.