1. 2.3 Distinctive features
The idea of Distinctive Features was first developed by Roman Jacobson ( ) in the 1940s as a means of working out a set of phonological contrasts or oppositions to capture particular aspects of language sounds.
Since then several versions have been suggested.

2. Some of the major distinctions include [consonantal], [sonorant], [nasal] and [voiced].
The feature [consonantal] can distinguish between consonants and vowels, so all consonants are [+consonantal] and all vowels [–consonantal].
[sonorant] distinguishes between what we call obstruents (stops, fricatives and affricates) and sonorants (all other consonants and vowels), with obstruents being [–sonorant] and others [+sonorant].
[nasal] and [voiced] of course distinguish nasal (including nasalized) sounds and voiced sounds respectively.

3. These are known as binary features because we can group them into two categories: one with this feature and the other without.
Binary features have two values or specifications denoted by ‘ + ’ and ‘ – ’ so voiced obstruents are marked [+voiced] and voiceless obstruents are marked [–voiced].

4. They are often written in shorthand forms as
The place features are not binary features – they are divided up into four values:
[PLACE: Labial]
[PLACE: Coronal]
[PLACE: Dorsal]
[PLACE: Radical]
They are often written in shorthand forms as
[Labial]p
[Coronal]p
[Dorsal]p
[Radical]p

7. A useful feature for consonants not found here is [±spread] (for ‘spread glottis’), which distinguishes between ‘aspirated’ and ‘unaspirated’ voiceless obstruents.
Aspirated sounds are [+spread] and unaspirated sounds are [–spread].
Now we can represent the rule that governs the unaspiration of /p/ after [s] in terms of features:

8.  [+spread] in other places
-cont
-voice
 [–spread] / [s]_____
 [+spread] in other places
This is a more general rule, which also applies to /t/ and /k/. It means that /p, t, k/ ([–voiced, –cont]) are all unaspirated ([–spread]) after [s] and aspirated ([+spread]) in all other positions.

9. Past tense forms in English
stopped, walked, coughed, kissed, leashed, reached
stabbed, wagged, achieved, buzzed, soothed, bridged
steamed, stunned, pulled
played, flowed, studied
wanted, located, decided, guided

10. The regular past tense form in English is pronounced as [t] when the word ends with a voiceless consonant, [d] when it ends with a voiced sound, and [ɪd] when it ends with [t] or [d].