This is a list of common frequency adverbs in English with rough estimates of their absolute frequency someone has posted on an ESL study site:

Always (100% of the time)
Frequently (about 90% of the time)
Usually (about 80% of the time)
Often (about 70% of the time)
Sometimes (about 50% of the time)
Occasionally (about 40% of the time)
Seldom (about 20% of the time)
Rarely (about 10% of the time)
Never (zero percent of the time)

Clearly, the usage of "never" (0%) and "always" (100%) as it relates to an absolute frequency would never be in question, but it is unclear if it is possible to say a given usage of a frequency adverb was correct if the exact absolute frequency or range of frequencies it represents were known.

For example, take the word "sometimes" - how would you know that 20% or 80% "of the time" would be a poor usage of the term, but 50% would be okay? Clearly, statically speaking there is a huge difference between 20% and 80% of the time, but it is unclear how a given frequency adverb's usage with an absolute frequency or frequency range would be accessed to be appropriate, or for that matter, inappropriate.

Is it ever possible to prove that the usage of frequency adverb is valid or invalid based on knowing the absolute frequency or range of frequencies it represents, and if so, how? Which is to say, is it possible to assign a range of frequencies to a frequency adverb and know they're correct, and if so, how?

If so, is the list referenced above correct, and if not, why?

• That's not the way language works. Bradd Szonye has pointed out problems with you table in particular; but there's another dimension of difficulty, in that meaning often depends on contextual and extra-linguistic factors, such as the social context and the degree to which the interlocutors know each other. Mar 30, 2014 at 0:18
• Not even close. Check out the situation with modals and negatives, for instance. It's not the quantifiers themselves, it's their usage in constructions. Any operator (quantifier, negative, modal) has a focus/bound element that it is connected to, and these can get twisted when there are several operators. Mar 30, 2014 at 2:20
• 'More often than not' can be useful. Mar 30, 2014 at 14:52
• Notice that a request for clarification related to the "onhold" flag applied to this question has been posted to Meta-English.SE here. Apr 1, 2014 at 15:04
• I have edited the post to make it more clear that you're asking about the validity of a list posted at an ESL study site, and not asking for people to opine about the meaning and usage of these words. Apr 2, 2014 at 4:10

Even as “rough estimates,” most of those figures are poor. For example, usually can mean anything between “more often than anything else” and “almost always.” It doesn't even necessarily mean a majority of the time. I'd say that sometimes and occasionally are much less common than the estimates above – but there are exceptions. Likewise, I'd say that frequently is less strong than usually, but it again depends on context.

None of these words are easily quantifiable, not even always and never, which often allow rare or minor exceptions. The words don't follow any kind of strict hierarchy or ordering either. Each has its own meaning.

In practice, all of the words have some overlap, but we can make some inferences from word choice. For example, when somebody says sometimes, we can guess that they didn't mean often or rarely, or they would have used those more specific words instead. But then again, sometimes people use sometimes to be vague (like I just did), so a lot depends on the context.

I have some problems. Consider

I visit my mother frequently, but I rarely see my brother these days.

This means I visit my mother 90% of what? The times I visit someone? I see my brother 10% of the time? That's rather a lot for a brother.

I know what you mean. But if you wanted to be precise you'd be using numbers in the first place.

Below my shot at non numerical quantification.

Always - As far as I can remember every time.

Frequently - Often enough to be annoying. I could even tell you how often. I go there on a regular *basis* with a constant frequency.

Usually - Most of the time but I cannot tell you exactly.

Often - Frequently enough to not be sometimes or seldom. It's my preferred option.

Sometimes - Unless there is another option.

Occasionally - When the occasion merits it yes, otherwise no.

Seldom - I have not been there in a long time. But yes I still go there.

Rarely - I'd only go there if I really need to.

Never - I'd never go there, you'd have to drag me there.

As you can see these are not absolute quantifiers but relative quantifiers.

To me the above table seems to be taken out of the air and I would like to know where it comes from. I would consider "seldom" and "rarely" as variants with the same meaning ( not very often) and I don't believe that any speaker ever thinks of a differentiation according to percentages.No speaker has statistic values in his pocket and choses adverbs of frequency according to percentages. The same is true for "often" and "frequently". They are variants with the same meaning. That table seems to come from someone who has no real knowledge of language.