English is one of the Earth's blandest languages, grammar-wise. Of course, it more than makes up for that in the convoluted spelling of its words. English is derived from at least six root languages, and history stirred them together until the late 15th century, when William Caxton began printing books in English, and devising spelling rules along the way. The language itself kept changing faster than the printers could keep up with spelling rules. Then came the Industrial and Scientific Revolutions, and many new words were added to the language. For many new words, people tried to spell them by following spelling rules. Sometimes, following spelling rules even produced an appropriate spelling for a new word. But this was not always the case.

It takes a special kind of person to be a spelling teacher, one who can present schoolchildren with a motley collection of heuristics and call them "rules" with a straight face. For a week or two, the student is content to follow these "rules", in the full flush of confidence that he or she finally has a grasp on how something works. It is a heady feeling. This, of course is the ideal point for the teacher to display the other job requirement, the sadism necessary to crush the student's confidence by presenting exceptions for every rule.

In this writeup, we will discuss a class of English words that are particularly troublesome to spell. These end with -ant, -ance, -ent or -ence.

There are, of course, words like want, pence, chant, and lance which just happen to end in one of these four combinations of letters. You'll probably think to yourself "these don't seem very difficult to spell", and, of course, they're not. But their longer cousins are difficult to spell, at least if you haven't memorized their spelling. Why?

The difficulty arises because most words use these combinations of letters as suffixes. -ant and -ent are pronounced identically, as are -ance and -ence. Why? Suffixes are almost always unstressed syllables, and because of that, a suffix's vowel generally degrades into a truncated 'u' sound, the schwa (ə).

When used as suffixes, -ant, -ance, -ent, and -ence turn a verb into a noun or and adjective:

-ant and -ent
usually form adjectives which describe their antecedent as a performer of the verb's action, or undergoing it. Sometimes they form nouns describing a performer of the action.
-ance and -ence
form nouns, which usually mean the quality of the verb's action being performed or happening.

The suffixes are usually applied to verbs that have survived the journey from Latin through Old French, Norman French, and Middle English into Modern English. In addition, there are several words derived directly from Latin which have been recently added to English as scientific and technical terms. Frequently, the verbs themselves didn't survive, but the nouns and adjectives formed from them did.

As some of you may know (and somewhat fewer care), Latin verbs fall into four basic classes describing their conjugation. In one of these classes of verbs (in fact called the "first conjugation"), the infinitive forms end in -are. In another class, infinitives end in -ere. This forms the basis of the suffix rules for most verbs: words derived from first conjugation verbs usually get -ant and -ance, the rest get -ent and -ence. But there are exceptions, even to this!

To add to the confusion, there is a class of words (which we will not list here) which end in -ment.

In the long run, we will have to throw up our arms and proclaim "there are no rules here!".

Because of that, and because it's not particularly useful for most people to have to learn Latin for the sole purpose of spelling words in English correctly, I will present a list of heuristics for you to ponder. In the list's examples you will find the most commonly confused words. But recall all I've said here: When in doubt, use a dictionary!

Gritchka points out a trick that works with a lot of words: Try to turn the problem suffix at the end of the word to -ent(i)al or -ant(i)al. The e or a is again pronounced, and you'll probably recognize one or the other as a real word. Thus, existence becomes existential, and substance becomes substantial.

Add -ant or -ance, when:

Root ends in hard C or G
elegant
significant

Exception: unguent (doesn't exactly fit the rule)
 
Root ends in Y
defy -> defiance
rely -> reliant
vary -> variance
apply -> applicant
dally -> dalliance
ally -> alliance
abeyance

Exception: mortify -> mortifacient
 
Root ends in -ear
clear -> clearance
forbear -> forbearance
 
Root ends in unstressed -er
aberrant, aberrance1
utter -> utterance

Exception: differ -> different, difference
Exception: belligerent
 
Root ends in -ure
assure -> assurance
endure > endurance
 
Begins with A
avoid -> avoidance
assist -> assistance
advance

Exception: advent
Exception: adherent
 
Root's last syllable contains A
react -> reactant (but see below)
 
Verb formed with a suffix containing an A:
supplicate -> supplicant
deviate -> deviant, deviance
dominate -> dominant, dominance
demonstrate -> demonstrance

Exception: violate -> violence
 
Others

please -> pleasant, pleasance
attract -> attractant
vigilance
stand -> stance, instant, instance
 

 
 

Add -ent or -ence, when:

Root ends in soft C or G:

innocent
reticent
intelligent
tangent
absence
reagent
suffice -> (in)sufficient, (in)sufficience
 
Exception: suppress -> suppressant
Exception: depress -> depressant
Exception: puissance
 
containing -esce
senescent, senescence
putrescent, putrescence
flourescent, flourescence
aquiescent, acquiescence
inflorescence
excresence
 
-cid-, -fid-, -sid-, -vid-
incident, incidence
coincide -> coincident, coincidence
confide -> confident, confidence
evident, evidence
subside -> subsidence
 
Exception: confidant (loanword)
 
-flu-, -qu-
Sequence, consequence
fluent, confluent, confluence
unguent

Exception: piquant (loanword)
 
Root ends in -ist
exist -> existent, existence
insist -> insistent, insistence
persist -> persistent, persistence
subsist -> subsistent, subsistence

Exception: assistance
Exception: resistance
 
Ends in stressed -er
refer -> referent, reference
infer -> inference
defer -> deference
prefer -> preference

Exception: bother -> botherance (whimsical construction)
Exception: (ab)errant1
 
Ends in -ere:
(in)(de)cohere -> (in)(de)coherent, (in)(de)coherence
adhere -> adherence, adherent
interfere -> interference

Exception: persevere -> perseverance
 
Verb built with suffixes beginning with E
intend -> intent (but see below)
pretend -> pretence (Brit.)
depend -> (in)dependent, (in)dependence

Exception: advent -> advance
Exception: intend -> intendant, intendance
 
Others
fend -> fence
defend -> defence (Brit.)
receive -> recipient
science, prescience, prescient
present, prescence (different etymology)
 

1This may actually be a case of people misapplying a rule in reverse. It's been pointed out to me that aberrant is pronounced with stress on the er, and sure enough, when I looked in the dictionary, that's what I saw. aberrant, prounounced this way, then becomes an exception for the stressed -er "rule" rather than an example of the unstressed -er "rule".

Carolyn's Corner: Spelling Observations Regarding Words Ending in -ant/-ent and -ance/-ence
http://www.spellingbee.com/cc04/Week19/observation.shtml

David Appleyard's Guide to Correct Spelling
http://www.davidappleyard.com/spelling.htm

Webster's New World Dictionary of the English Language, Second Collegiate Edition, 1979, William Collins Publishers