# Thread: rotation of a cylinder

1. ## rotation of a cylinder

dear friends,

how are you?

What's the difference between...

- rotative cylinder
- rotary cylinder

Thank you.

2. ## Re: rotation of a cylinder

Originally Posted by marciobarbalho
dear friends,

how are you?

What's the difference between...

- rotative cylinder
- rotary cylinder

Thank you.
'Rotative' is much the rarer word (if it's a word at all - I haven't ever met it). If I saw the two words used in a contrastive sense, I'd think that 'rotative' means that it can go round and 'rotary' means that it does (or contains something that does) go round:

Wänkel invented a rotary engine./ Many people now prefer to use a rotary mower, but a cylinder mower produces a neater finish.

Hmm, confusing example. The cylinder, or roller, in a cylinder mower also goes round. C'est la langue.

I've provided no examples of 'rotative' because I know of none.

b

3. ## Re: rotation of a cylinder

A dictionary defines rotating as being:

and rotary as:

adj. Of, relating to, causing, or characterized by rotation, especially axial rotation.

Could we say that 'rotary' and 'rotating' (as adjectives) are fully interchangeable?

Thanks

4. ## Re: rotation of a cylinder

[QUOTE=marciobarbalho;536259]A dictionary defines rotating as being:

.../QUOTE]

Which one? Something that is not going round is not rotating, whatever its shape. I wouldn't use 'rotating' and 'rotary' interchangeably.

b

5. ## Re: rotation of a cylinder

so, rotating cylinder would be awkward?

Thanks

6. ## Re: rotation of a cylinder

Originally Posted by marciobarbalho
so, rotating cylinder would be awkward?

Thanks
Not at all, as long as it was going round.

b

7. ## Re: rotation of a cylinder

Hmm... I am kinda confused now...

How would I tell them apart?

8. ## Re: rotation of a cylinder

Originally Posted by marciobarbalho
...
and rotary as:

adj. Of, relating to, causing, or characterized by rotation, especially axial rotation.

...
This definition is OK. Something that is rotary may be still, but it will turn if it moves. Something that is rotating is actually going round.

b

9. ## Re: rotation of a cylinder

Hi! I'm not a native speaker nor a teacher of English, but I've studied Aeronautics for over 5 years now and know a little about engines.
In my opinion, in technical language 'rotary' and 'rotating' almost always mean the same thing: it operates by moving about an axis, for example, although the latter does tend to refer to constant rotation (e.g.,rotating airframe missile) while the former does not(a Boeing Rotary Launcher can rotate but only does so when needed) .Most likely what you referred to was the Wankel engine, this being the most famous example.
But this does not necessarily extend outside the field of technical language. Why don't you give us a context (in which you found those 'rotary' and 'rotative' thing)to work with? This may clear things up a bit.

10. ## Re: rotation of a cylinder

Originally Posted by Spetsnaz26
Why don't you give us a context (in which you found those 'rotary' and 'rotative' thing)to work with? This may clear things up a bit.
Well... it's just a cylinder, a solid flows inside of it and a chemical reaction takes places, so we need to rotate the cylinder to improve conversion yield...long story.

but...here comes the question... I have seen people (non-natives, like me, usually like to made up some words based on their mother-tongues, no offense to others, please) use these adjectives to describe such cylinder (or reactor, if you will):

rotatory
rotative
rotary
rotating

They are all right, but I am not sure which one is more appropiate, all I want is to make it sound natural.

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