Long is an adjective or an adverb.

We can use long to talk about time, distance or length.

Time

We use long as an adverb in questions and negative clauses to talk about duration:

A:

How long has Valerie been staying with you?B:

She arrived in January, so she’s been here for four months.

Marco didn’t stay long at the party.

Don’t be long.

Warning: 

We don’t use long on its own in affirmative clauses. We often use (for) a long time:

We waited for a long time in the rain for the bus.

Not: … waited long …

They took a long time getting here.

Not: They took long …

We can use long in affirmative clauses with too, enough and so:

A month is too long to wait for an appointment.

We’ve waited long enough for a reply. I think we need to phone them.

You took so long. What were you doing?

When we talk about actual amounts of time, we can use phrases with time + long, or phrases like all day long, all month long:

The lecture was three hours long.

We worked all day long.

We can also use a long time ago, long ago or long before to refer to a time many years in the past:

This castle was built a long time ago. (or … was built long ago.)

Long before you were born, there was a factory here. It was closed in the 1960s.

We use long as an adjective:

You’re home already. That can’t have been a very long film.

Distance

We can use the phrase a long way to talk about distance:

My house is a long way from the station. You’ll have to take a taxi.

It’s a long way to the nearest petrol station.

In negative statements and questions we usually use far:

My house is not far from the station.

Is it far to the beach?

Length

We use long to talk about the length of something:

It was three metres long and four metres wide.

How long is the boat?

This is such a long queue. It’s going to take at least an hour.

As long as

The phrase as long as is used as a conjunction. It means ‘on condition that’:

As long as the weather is okay, we’re going to paint the house tomorrow.

Jenny said she’d come to the party as long as we don’t stay too late.

No longer and not any longer

We can use the phrases no longer and not … any longer to refer to something that used to exist or happen but does not exist or happen now:

There are no longer any family bakeries in our town.

A:

Are you still working at the garden centre?B:

No, not any longer.

Typical error

• We can’t use long on its own in affirmative sentences:

A:

Will it take long?B:

No, it won’t take long. (or Yes, it’ll take a long time.)

Not: Yes, it’ll take long.

Only

Only is an adjective or adverb.

Only as an adjective

We use only as an adjective to mean that there is just one or very few of something, or that there are no others:

He was the only person in the room.

Being healthy is the only thing that is important to me.

Only as an adverb

We use only as an adverb to mean that something is limited to some people, things, an amount or an activity:

This phone is only available in Japan.

Only a few hundred houses survived the hurricane without any damage.

Only can mean ‘simply’:

He’s only joking.

Spoken English: 

In speaking, only can be used with just for emphasis. It can mean ‘very recently’ or ‘almost not’:

She’d only just moved into her new house last July.(very recently)

The building had survived the earthquake of two years before, but only just. (It almost didn’t survive the earthquake.)

Only: position

As an adjective, we use only in front of a noun or one, or before another adjective or a number:

Is that your only copy of the book?

He was the only one who could read in the village.

Not: He was the only who could read …

That was the only large t-shirt left in that colour.

There were only four United fans in the room.

We can use only as an adverb in different positions, depending on its focus. If the subject is the focus, we put only in front position:

Only Jason knows where the key is kept.

Only a very small bed will fit in this room.

If the focus is on another part of the sentence, we usually put only in the normal mid position for adverbs (between the subject and the main verb, or after the modal verb or first auxiliary verb, or after be as a main verb):

I only go home once a month. (between subject and main verb)

She had only arrived at midnight the night before.(after the first auxiliary verb)

She’s only sixteen. (after be as a main verb)

If the focus is a whole clause, we can put only in front position:

My arm hurts but only when I try to raise it.

Same, similar, identical

Same means that two or more things are exactly like one another. We can use same as an adjective before a noun or as a pronoun. When we use same to compare people or things, we must use it with the:

I noticed that Richard and I were both wearing the same jacket.

Not: … were both wearing same jacket.

These two colours are not the same. This one is slightly lighter than that one.

Not: … are not same.

The same as

Warning: 

The same is followed by as. It is not followed by that or than:

Does ‘start’ mean the same as ‘begin’ in English?

Not: … the same that … or … the same than…

My new car is the same model as my old one.

Not: … the same model that … or … the same model than …

The same + noun + clause

When we use the same with a noun, we can follow it by a clause with that, and less commonly with who or which. We can often leave out that, who or which:

She’s the same person (that) I spoke to when I phoned their office.

How was the course? Was it the same teacher (who) you had last time?

We can emphasise same with very:

This is the very same hotel we stayed at when we were here twenty years ago!

Do the same

We can use do the same instead of repeating a clause:

She bought her ticket for the folk festival online, and we did the same. (We also bought our tickets online.)

Similar and identical

We use similar if two or more things are not entirely the same, or identical if two or more things are exactly the same. We use the patterns similar to and identical to, a similar + noun or a similar + one and an identical + noun or an identical + one. We don’t say a same:

This colour is similar to that one.

Frank had a problem connecting his printer. We had a similar problem, so it must be the software.

Not: … a same problem …

She first showed us a beautiful 16th-century vase. Then she showed us an identical one, but the second one was a copy.

Not: … a same one …

Questions 1 and 2 were identical.