You have three words: absorb, absorbed, absorption.  Why does the 'b'
turn into a 'p' in absorption?

Hi barbara817,

In linguistics, the phenomenon is called "regressive voicing assimilation."

"B" is a voiced consonant (a sound made when the vocal cords are
vibrating), while "p" is a voiceless consonant (made when the vocal
cords are not vibrating).

"Voiced and Voiceless Speech Sounds," by Kenneth G. Wilson  (The
Columbia Guide to Standard American English, 1993)
Bartleby.com
http://www.bartleby.com/68/6/6406.html

"B" and both "t" and the "sh" sound in "-tion" differ in voicing: "b"
is voiced, while "t" and "sh" are voiceless.  (Try saying "sh"; your
vocal cords won't vibrate, as opposed to, for example, a "z" sound.) 
Regressive voicing assimilation requires such consonants, when placed
adjacent to each other, to agree in voice.  So the "b" (voiced)
becomes a "p" (voiceless) when placed next to the "t" in "-tion." 
Other examples are [describe > description] and [scribe >
script/scripture].

"Structure of English II: The Word -- Phonology: Voicing
Assimilation," by S. Hurvitz, S. Farby
Yehuda N. Falk, Senior Lecturer in English Linguistics, Department of English
The Hebrew University of Jerusalem
http://pluto.mscc.huji.ac.il/~msyfalk/WordStructure/Voicing.pdf

"Voicing and devoicing in English, German, and Dutch; evidence for
domain-specific identity constraints," by Janet Grijzenhout (pp. 8-9)
Theorie des Lexicons (Theory of the Lexicon), Philosophische Fakultät
der Heinrich-Heine-Universität Düsseldorf
http://www.phil-fak.uni-duesseldorf.de/sfb282/working_papers/sfb116-voice.PDF

Google cache of "Word-Faithfulness and the Direction of
Assimilations," by Toni Borowsky, University of Sydney (scroll down to
example 14 d)
Philipps-Universität Marburg
http://64.233.167.104/search?q=cache:vj_FxHVFSI0J:pc0880.germanistik-kunst.uni-marburg.de/~roa/OT-TEXTS-archive/362-1199/362-11991.doc

Perhaps only a linguist or linguistics student could give you a
complete explanation.  But I hope this explanation gives you a sense
of why "absorb" turns into "absorption."

- justaskscott


I used many search terms on Google, in various combinations, including:

absorb
aborption
describe
description
scribe
script 
scripture
linguistics
phonetics
assimilation
voiced
voiceless
b
p
voicing
"regressive voicing assimilation"
"regressive assimiliation"

---

Clarification of Answer by justaskscott-ga on 20 Jan 2005 14:14 PST

And note that the "d" sound is voiced, which would explain why "b"
(also voiced) remains "b" in "absorbed."

This may be of interest to you:

"The word 'absorb' was originally derived from Latin 'absorptus' and
used to be commonly spelled with a P. In such forms as 'absorped' and
'absorping' the P shifted to a B; but in the more scholarly word
'absorption' the P remained."

http://64.233.179.104/search?q=cache:qQIL-bKIkYYJ:www.nmia.com/~soki/errors.rtf