Linguists divide language into the lexicon (an inventory of its morphemes) and its grammar (the rules which govern how those morphemes are combined into lexemes, phrases, and sentences). A morpheme is an abstract, minimal unit of meaning (or a sign in the Sassurean sense). The sentence: "He walked" consists of three morphemes, i.e., HE, WALK, and -ED. (It's a convention to write morphemes in all caps to distinguish between them and actually sequences of sounds in speech and writing.) What about the sentence "He won"? How many morphemes in that? Three: i.e., HE, WIN, and -ED. For most verbs, there is a grammatical rule that stipulates that the third person, preterite form of a verb is constructed by adding the morpheme -ED to the verb: e.g., WALK + -ED ==> walked. What about the irregular verbs? Usually, the irregular forms are stored in the lexicon as is: won <== WIN + -ED. As with most things in language, it's a little more complicated than this brief overview would suggest. For example, the actually sounds that result from putting together morphemes changes in some deterministic ways. For example, to make the plural in English, add the -S morpheme to the noun: e.g., LIGHT + -S, DOG + _S, and JUDGE + -S. If we look at the words lights, dogs, and judges in their phonological representation we'll see: /laɪts/, /'dɔgz/, and /'ʤʌʤɪz/. The -S morpheme is rendered phonologically in different ways depending on whether the phoneme that the noun ends with is voiceless or voiced (the difference between /t/ and /g/ or whether it's manner of articulation is a stop /t/ and /g/, or a (af)fricative /ʤ/. Not all syllables end in a consonant. What about words like law. How does the -S morpheme get rendered in this case? /'lɔz/. This still fits our rules above, because English doesn't have voiceless vowels (something other languages do, e.g., Japanese), the -S is rendered as a voiced /z/. Another thing you find in the lexicon are compounds and idiomatic phrases. This makes sense because the meaning of many of these constructions cannot be determined by the meaning of their constituent parts and the rules of how they are combined. For example, the phrase "the big book" is easily determinable from the meanings of the three morphemes which make it up, but "to kick the bucket" is not.

I realize that I can look this up, but since this is a course, can you please tell me what preterite is? WALK and ED are 2 morphemes, so would HAD WALK ED be 3? Would "HE HAD BEEN A GOOD FRIEND" have 6 morphemes?

Isn't HAD two: HAVE ED?

preterite

I was using it for the simple past tense in English. It's a little old-fashioned, but it's what I learned in grammar school.

"He had been a good friend" contains eight morphemes: HE, HAVE, -ED (past tense), BE, -EN (past participle), A, GOOD, and FRIEND. The phrase, HAVE + -ED BE + -EN is usually called the past perfect tense (pluperfect, plusquamperfectum) of to be. (A side note: plus quam perfectum means 'more than perfect' in Latin; that's the sort of construction that usually sends peevologists over the top, but here it is perfect grammatical and meaningful.)