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# 9.14: The Prefixes ob- and dis- and More Work with Bound Bases

Difficulty Level: At Grade Created by: CK-12

## The Prefixes ob- and dis- and More Work with Bound Bases

1. The prefix ob- usually adds the meaning “to, toward, on, over, or against.” The <b>\begin{align*} <\mathrm{b}> \end{align*} in ob- assimilates fully or partially when ob- is added to certain stems. Analyze each of these words as instructed. Each word starts with a form of ob-:

Word = Prefix + Stem
offer = ob\begin{align*}\cancel{b}\end{align*} + f + fer
object = ob + ject
obstruct = ob + struct
opportunity = ob\begin{align*}\cancel{b}\end{align*} + p + portunity
occur = ob\begin{align*}\cancel{b}\end{align*} + c + cur
omit = ob\begin{align*}\cancel{b}\end{align*} + + mit
omission = ob\begin{align*}\cancel{b}\end{align*} + + mission

2. The prefix dis- usually means either “lack of, not” as in disorder and dishonest, or “removal, reversal” as in disassemble. Usually the prefix dis- is added to a stem by simple addition, but sometimes the <s>\begin{align*} <\mathrm{s}> \end{align*} assimilates fully or partially. Each of the following words contains some form of the prefix dis-. Analyze each word as instructed:

Word = Prefix + Stem
discontent = dis + content
difficult = dis\begin{align*}\cancel{s}\end{align*}+ f + ficult
discomfort = dis + comfort
directing = dis\begin{align*}\cancel{s}\end{align*}+ + recting
divides = dis\begin{align*}\cancel{s}\end{align*}+ + vides
discontinue = dis + continue
division = dis\begin{align*}\cancel{s}\end{align*} + vision
disproof = dis + proof
divorced = dis\begin{align*}\cancel{s}\end{align*}+ + vorced
disappoint = dis + appoint

3. Each of the following words contains a bound base and a prefix. Some contain a suffix. Analyze each word:

Word = Analysis
convict = com\begin{align*}\cancel{m}\end{align*} + n + vict
exploring = ex + plore\begin{align*}\cancel{e}\end{align*}+ ing
congress = com\begin{align*}\cancel{m}\end{align*} + n + gress
correct = com\begin{align*}\cancel{m}\end{align*} + r + rect
suggest = sub\begin{align*}\cancel{b}\end{align*}+ g + gest
objects = ob + ject + s
respectful = re + spect + ful
indictment = in + dict + ment
announcer = ad\begin{align*}\cancel{d}\end{align*} + n + nounce\begin{align*}\cancel{e}\end{align*} + er
instructing = in + struct + ing
collected = com\begin{align*}\cancel{m}\end{align*} + l + lect + ed
suffering = sub\begin{align*}\cancel{b}\end{align*}+ f + fer + ing
elects = ex\begin{align*}\cancel{x}\end{align*} + lect + s
editor = ex\begin{align*}\cancel{x}\end{align*} + dit + or
consisting = com\begin{align*}\cancel{m}\end{align*}+ n + sist + ing

4. The bound base spect means “look at, see.” Sometimes when prefixes are added to spect unusual assimilations take place. Each word contains the bound base spect. Analyze each word into its prefix and stem:

Word = Analysis
suspect = sub\begin{align*}\cancel{b}\end{align*} + spect
prospect = pro + spect
aspect = ad\begin{align*}\cancel{d}\end{align*} + spect
inspect = in + spect
respect = re + spect
perspective = per + spect
expect = ex + s\begin{align*}\cancel{s}\end{align*}pect

Teaching Notes.

Item 1. The assimilation pattern for ob- is consistent with the general tendency to avoid juxtaposing voiced and voiceless consonants. The pattern can be described as follows: (i) Ob- assimilates fully before <c>, <f>, and <p>\begin{align*} <\mathrm{p}> \end{align*}; (ii) it assimilates partially, to o-, before <m>; (iii) it assimilates partially to os- before <t>: ostensible (ob\begin{align*}\cancel{\mathrm{b}}\end{align*} + s + tense\begin{align*}\cancel{\mathrm{e}}\end{align*} + ible), ostentatious (ob\begin{align*}\cancel{\mathrm{b}}\end{align*} + s + tent + atious); (iv) elsewhere it follows the rule of simple addition. There are a very few frequently used holdouts to this pattern, involving simple addition though it juxtaposes the voiced [b] with a voiceless consonant: obtain, obstinate, obfuscate, and probably obscene. A number of recent and technical formations also follow simple addition. For more on ob-, see AES, pp. 195-96.

Item 2. The assimilation pattern for dis- can be described as follows: (i) Dis- assimilates fully before <f>; (ii) it assimilates partially, to di-, sometimes before <d>, <g>, <j>, <sc>, and <sp>, more often before <l>, <m>, <r>, <st>, and <v>; (iii) elsewhere it follows the rule of simple addition. For more on dis-, see AES, pp. 193-94.

Item 4. The <s>\begin{align*} <\mathrm{s}> \end{align*}-deletions in suspect and aspect are consistent with a weak constraint in English against double consonants within strings of three or more consonants: The normal assimilation of sub + spect would lead to *susspect; that of ad + spect would lead to *asspect, both with <ss>\begin{align*} <\mathrm{ss}> \end{align*} in the three-consonant string <ssp>. For more on this doublet constraint, see AES, pp. 77-80. As discussed earlier, the <s>\begin{align*} <\mathrm{s}> \end{align*} deletion in expect is due to the fact that <x> spells [ks], making the <s>\begin{align*} <\mathrm{s}> \end{align*} redundant. See the teaching notes and item 3 in Book 5, Lesson 12.

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