Alongoralongside?

As apreposition,alongmeans ‘in a line next to something long and thin’, e.g. a road, a path:

There were lots of shopsalongthe main street.

I saw three different boatsalongthe bank of the river.

We usealongas an adverb with verbs of motion meaning ‘together with’:

Why don’t you comealongwith us to the party?

They said they’d bring the bikesalongand we can ride to the swimming pool.

As a preposition,alongsidemeans ‘close beside’, ‘next to’ or ‘together with’:

The treesalongsidethe fence have all been damaged by the wind.(near)

Put your bikealongsidemine.(next to)

I find it difficult to cope with this illnessalongsideall my other problems.(together with)

We also usealongsideas an adverb, meaning ‘along the side of’ or ‘next to’ something:

I parked my car in the drive and William parked hisalongside.