We take any number of segments, each of which is complementary to every other one we have taken, and say that they comprise a single class which we call a phoneme (writing its symbol between slating lines). E.g. segments [K, k, K] can all be included in a phoneme /k/. Each of the mutually complementary sets of 7.22 [Summing over the Environments] may thus constitute a phoneme by itself.
- Harris (1951), a pag.61

If every environment had the same number of segments which contrasted in it […] each phoneme would consist of one segment from each environment, and the number of different phonemes would be the number of contrasting segments in any environment.
- Harris (1951), a pag.64

[…] phonemes will be defined as groupings of segments […].
- Harris (1951), a pag.64

Since the phonemes are to be defined not merely as consisting of particular segments, but as consisting of particular segments each in a particular environment, it will be convenient to group the segments in such a way that several phonemes, especially such as have similarities of phonetic symmetry or may otherwise be grouped together, should have roughly identical total environments.
- Harris (1951), a pag.68

The elements of our utterance are now phonemes, each being a class of complementary segments-per-environment.
- Harris (1951), a pag.72

There will be several phonemes occurring at the ends of morphemes which have a consistent difference as compared with an equal number of phonemes which do not occur at the ends of morphemes: there will be non-released [t’], [k’], etc., as compared with released [t], [k], etc.
- Harris (1951), a pag.88

In many languages we will find […] that one phoneme or another does not occur in particular environments in which other phonemes do, even when those phonemes are in general similar to it in distribution. This results from the fact that in some cases we may be unable to group segments into phonemes in a way that would satisfy the criteria of 7.4 [Criteria for Grouping Segments], because there are too many or too few distinct segments recognized in a given environment, or because two segments which we would like to group together happen to contrast.
- Harris (1951), a pag.90

The phonemes […] represent particular segments in particular environments, the relation of segment to environment being always the same: the occupancy of a unit length within a succession of unit lengths.
- Harris (1951), a pag.134

[…] phonemes are symbols of relation among segments.
- Harris (1951), a pag.135

[…] the phonemes of a language could be described as marking the independent distinction among utterances […].
- Harris (1951), a pag.135, n.21

In writing utterances by means of phonemes, or in discussing the distribution of phonemes, only the sequence of phonemes mattered: it followed from the definition that every phoneme occupied only one unit length and that in each unit length only one phoneme occurred.
- Harris (1951), a pag.136

[…] the phonemes (and their respective members) indicated by a phoneme-class mark are precisely the ones which contrast in the environment in which the phoneme-class occurs.
- Harris (1951), a pag.151, n.1

Certain phonemes or phoneme sequences may occur only in […] short morphemes, or in other morphemes which are marked by some special distributional or phonemic feature.
- Harris (1951), a pag.174

[…] we can say that every phoneme has some elementary meaning in that it differentiates one meaning-correlated morpheme from another: we can say that /t/ correlates with the meaning difference between 'short' and 'shorn', 'shore', etc., and between 'take' and 'lake', 'ache', etc., and so on. In linguistic systems I which phonemes are restricted as to their neighbors, it is also possible to say that the phonemes have certain expectation value: after the English phonemes /par/ adding the phoneme /č/ permits us to expect the phoneme /d/ and the utterance 'parched', or the phoneme /m/ and the morpheme 'parchment', and so on, but not, say, the phoneme /z/.
- Harris (1951), a pag.188, n.66

[…] our phoneme becomes the expression of two independent relations: primarily relation of complementary distribution (plus free variation); secondarily the morphophonemic relation of substitutability in various members of a morpheme.
- Harris (1951), a pag.233

Utterances or parts of them are considered equivalent to each other if they are repetitions of each other; they are distinct from each other if they are esplicitly not repetitions […]. Parts which are not distinct from each other are then grouped into classes in such a way that all the members of a particular class either substitute freely for each other in stated environments […] or are complementary in environment to each other […]. When the grouping is such that the distinctions between classes are in one-one correspondence with the distinctions between contrasting (i.e. distinct) segments, the classes are called phonemes.
- Harris (1951), a pag.361