Learn English – difference between progress ON and progress OF

@RegDwight is correct in every particular. Till is indeed older and the two can be used pretty much interchangeably.

There is really only one usage I can think of where you would not use till: in setting up a negative conditional.

Until my landlord fixes the plumbing, I am not going to pay the rent.

I am not going to pay the rent until my landlord fixes the plumbing.

Here it would sound strange to use till, and I'm not really sure why. Perhaps it is the negative.

One more thing. Sometimes you will see people spell till as a contraction of until: that is, as 'til. This is simply wrong, and not seen outside of old poetry and modern greeting cards aiming for a "poetic" tone. Anywhere you see 'til being used, till would be the correct word.

The way these prepositions are used in these examples has nothing to do with the fact that "categorize" occurs in the sentence.

• 1: "in" is part of the adverbial phrase "in many different ways". This could be apt for a multitude of main verbs. "He painted in many different ways." "they walked in many different ways". There's nothing special here with regard to using "in" with "categorize", even though they are collocated.

• 2: this is a shorter adverbial phrase "as conservative". If I inderstand the terminology, "as" links a stative verb with its predicate adjective. This usage fits a narrower range of main verbs, such as "viewed", "seen", "tagged", "understood". (See http://www.google.com/search?q=define+as&ie=UTF-8&oe=UTF-8&hl=en , meaning 1 for prepositional use of "as")

• 3: "in this field guide" is, as in #1, an adverbial phrase that could be applied to many verbs. "There are many pictures in this field guide." "John Muir was quoted in this field guide." As in #1, there's nothing instructive here with regard to using "in" with "categorize", but in this example they are not collocated; "in" is NOT being used WITH "categorized".

But what you should have noticed, and bolded, in this example, is by—this is the preposition associated with "categorized". In this example, "by" is used in the third bulleted meaning under the #3 sense for the Preposition ("parameter") HERE http://www.google.com/search?q=define+as&ie=UTF-8&oe=UTF-8&hl=en&#hl=en&q=define+by

A few verbs that collocate with "by" in this sense (I'm sure there must be more):

• sort by ...

• classify by ...

• organize by...

• assign to [x] by...

• group by...

• alphabetize by {name/state/city/etc}

In such cases "by" can be understood as rougly equivalent to "according to".