Learn English – Ability in the future: Can vs Will be able to

The form, X is [number] times the size of Y always means X is [number] times bigger than Y.

The form, [number] times smaller is perfectly acceptable, clear (not ambiguous in any way), and is often more popular or even the only idiomatic form in common usage. I'll call this the Times Smaller Form. The preference (aka "popularity") for this usage (instead of the Fraction Form) grows as [number] gets bigger. This is demonstrated in the following Google Ngrams.

Google Ngram Three, Four
In these Ngrams, positive values means the Times Smaller Form is more popular and negative values means the Fraction Form is more popular. (See footnote #1 for an explanation of the Ngram equations.¹) Note above that the only instance (in this Answer) where the Fraction Form is more popular than the Times Smaller Form is "one third the size". In all other cases (in this answer), the Times Smaller form is more popular.

Google Ngram Five, Ten Note that these are at about 50%, which is higher than three and four.

Google Ngram One Hundred, One Thousand Again, these are higher than the prior ngrams. +100% here means all instances are in the Times Smaller Form. The Fraction Form is non-idiomatic in this case.

Google Ngrams for Ten Thousand and One Million also show +100% of usage is in the Times Smaller Form indicating this is virtually an idiomatic form. On the other hand, it's grammatically correct to say "ABC is one ten-thousandth the size of XYZ". Interestingly, the Fraction Form doesn't strike me as odd or wrong in any way, but the searches in Google Ngram (and various corpora at http://corpus.byu.edu/) suggests this usage is rare.

Also note that the Times Smaller Form has even more usage than shown here since it has two variants for large numbers: a hundred times smaller, one hundred times smaller, a thousand times smaller, one thousand times smaller, etc. For example, it's natural to say "This is a thousand times smaller than that." See Google Ngram Variants

FOOTNOTE 1: Normalizing Google Ngram results.

In these Google Ngrams (A - B)/(A + B) shows a normalized difference from -1 to 1 (shown by Google Ngram as -100% to 100%).

• In all Ngrams, A = Times Smaller Form, B = Fraction Form
• 0% means "no difference" in popularity between the two terms.
• Positive values mean the first term (A, the Times Smaller Form) is more popular.
  (A value of +100% means there are only instances of A.)
• Negative values mean the second term (B, the Fraction Form) is more popular.
  (A value of -100% means there are only instances of B.).

This method allows us to compare widely different result-counts on a common scale.

• Pair #1 is A=15, B=5.
• (15 - 5) / (15 + 5) = 10 / 20 = 50%.

• The difference 10 is 50% of the total 20.

• Pair #2 is A=3000, B=1000

• `(3000 - 1000)/(3000 + 1000) = 2000 / 4000 = 50%
• The difference 2000 is 50% of the total 4000.

Even though Pair #2 is far more common than Pair #1, they both demonstrate that A is more popular than B, and in the same relative ratio. A potential weakness is that smaller result counts are less accurate. For example, A=3, B=1, also results in 50%, but this would be too small to be reliable.

There are a number of things going on in this question. Having read it over a couple of times together with the additional information in the OP’s comments, I think the best way to approach it is case-by-case.

First though it’s worth mentioning that while the OP has pointed out in a number of comments that the question is not about etiquette, it’s not that simple. When dealing with introductions there are established rules of etiquette that we have been trained to follow, whether we do that consciously or sub-consciously is not important, what is important is that they are there and that they do not always sit comfortably with other ‘normal’ usage.

…this is Tom Smith, our business partner; and this is Jim Blake, our lawyer.

First question – Can we do without the additional ‘this is’?

… this is Tom Smith— our business partner, and Jim Blake— our lawyer.

Generally yes. There are only two exceptions that I can think of; one comes later and the other is where a group is being presented and the person that they are being presented to, often a VIP of some type, makes a comment or asks a question after each name. Think of a royal reception where an elderly Royal makes a politically incorrect statement before moving on to the next embarrassed celebrity. In that case the introduction process resets and you would start again with a ‘This is’

In the same way that I turn to The OED for guidance on etymology and usage, for the definitive guide on matters of etiquette I head to Debrett’s:

Mary, this is Jim Wilson, Bob Aspinall and Sue Godstone.

As an aside, notice that Debrett’s is very keen that you should always make introductions two-way, completing the above example with “Everyone, this is Mary Brett”

Next, this vs these

OK, this is where it gets complicated.

The general rule is that you follow normal rules of grammar – this for individuals, these for groups

This is Mike from accounting

This is my neighbour, john Smith.

These are my classmates, Peter, Paul and Mary

You enter a minefield though when you start dealing with groups that can be thought of as a single entity:

and these are the other band members, Paul, George and Ringo

and this is the rest of the band: Paul, George and Ringo

Are both acceptable.

Finally we come to couples and here all the rules change, or rather, they fall apart. Mary Bryant, a writer on weddings and general etiquette starts with the following:

Couples are introduced separately, although it is advisable to clarify the relationship (‘And this is Sarah, Peter’s wife/girlfriend’).

We’ve gone back to an additional ‘this is’….

However, it is also common practice to introduce a couple as a single entity - The reference found for ‘this is’ in Collins is correct in this instance

This is Mike and Sue Jones who live next door (A couple as a single entity)

Although….

These are our neighbours, Mike and Sue Jones (The same couple, now plural as neighbours)

I started off by saying that we can’t ignore etiquette and I stand by that. But etiquette, like dialect is only another form of usage, another set of rules – confusing and often contradictory.