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8.13: The Prefix Ob-

Difficulty Level: At Grade Created by: CK-12

The Prefix Ob-

1. You have seen that when certain prefixes are added to certain stems, the last consonant in the prefix assimilates. In each of the following words, the first two letters are some form of the prefix ob-. Analyze each word to show what happened when the prefix ob- was added to the stem:

Word = Prefix + Stem
opposite = ob\begin{align*}\cancel{b}\end{align*} + p + posite
object = ob + ject
observe = ob + serve
occupy = ob\begin{align*}\cancel{b}\end{align*} + c + cupy
offer = ob\begin{align*}\cancel{b}\end{align*} + f + fer
obtain = ob + tain
opportunity = ob\begin{align*}\cancel{b}\end{align*} + p + portunity
occur = ob\begin{align*}\cancel{b}\end{align*} + c + cur
obstacle = ob + stacle
occupation = ob\begin{align*}\cancel{b}\end{align*} + c + cupation
obvious = ob + vious
oppose = ob\begin{align*}\cancel{b}\end{align*} + p + pose
oblige = ob + lige
occasion = ob\begin{align*}\cancel{b}\end{align*} + c + casion
offense = ob\begin{align*}\cancel{b}\end{align*} + f + fense

2. Now sort the twelve words into these two groups:

Words in which the
assimilated: did not assimilate:
opposite oppose object
occupy occasion observe
offer offense obtain
opportunity obstacle
occur obvious
occupation oblige

3. Now sort the nine words in which the <b>\begin{align*}<\mathrm{b}>\end{align*} assimilated into these three groups:

Words in which
<c> <f> <p>\begin{align*}<\mathrm{p}>\end{align*}
occupy offer opposite
occur offense opportunity
occupation oppose
occasion

Word Spell. How many words of three letters or more can you spell from the letters in the word opportunity! There are more than a hundred possible ones.

O P P O R T U N I T Y

Teaching Notes. Here are some of the possible words:

inputintointroion pointy pony poor pop  rot  rout  ruin  run  tun  turn  turnip  tut\begin{align*}& \text{input} && \ \quad \text{pointy} && \ \ \text{rot} && \ \ \text{tun} \\ & \text{into} && \ \quad \text{pony} && \ \ \text{rout} && \ \ \text{turn} \\ & \text{intro} && \ \quad \text{poor} && \ \ \text{ruin} && \ \ \text{turnip}\\ & \text{ion} && \ \quad \text{pop} && \ \ \text{run} && \ \ \text{tut}\end{align*}

ironironynipnippynitnittynornorinotnutnuttyoptoptionortouroutoutpointpinpinotpintpinuppinypionpionpippitpitonpitypoipointportportionpotpotionpottypourpoutpoutyprintprintoutprionprontopropprotonprypunpunitorypuntpuntypunnypurityputputtputtputtyriotriprootrootyropyruntruntyrutruttytintinttinytiptippytiptoptirotootoontoottoptortorntorttottourtoytriotriptriptritontrooptrottrouttrytryouttutortypotyrounitunityunripunrootuntouponuppityuprootyipyonyouyouryour\begin{align*}& \text{iron} && \text{port} && \text{runt} && \text{tutor} \\ & \text{irony} && \text{portion} && \text{runty} && \text{typo} \\ & \text{nip} && \text{pot} && \text{rut} && \text{tyro} \\ & \text{nippy} && \text{potion} && \text{rutty} && \text{unit} \\ & \text{nit} && \text{potty} && \text{tin} && \text{unity} \\ & \text{nitty} && \text{pour} && \text{tint} && \text{unrip} \\ & \text{nor} && \text{pout} && \text{tiny} && \text{unroot} \\ & \text{nori} && \text{pouty} && \text{tip} && \text{unto} \\ & \text{not} && \text{print} && \text{tippy} && \text{upon} \\ & \text{nut} && \text{printout} && \text{tiptop} && \text{uppity} \\ & \text{nutty} && \text{prion} && \text{tiro} && \text{uproot} \\ & \text{opt} && \text{pronto} && \text{too} && \text{yip} \\ & \text{option} && \text{prop} && \text{toon} && \text{yon} \\ & \text{ort} && \text{proton} && \text{toot} && \text{you} \\ & \text{our} && \text{pry} && \text{top} && \text{your} \\ & \text{out} && \text{pun} && \text{tor} && \text{your}\\ & \text{outpoint} && \text{punitory} && \text{torn} \\ & \text{pin} && \text{punt} && \text{tort} \\ & \text{pinot} && \text{punty} && \text{tot} \\ & \text{pint} && \text{punny} && \text{tour} \\ & \text{pinup} && \text{purity} && \text{toy} \\ & \text{piny} && \text{put} && \text{trio} \\ & \text{pion} && \text{putt} && \text{trip} \\ & \text{pion} && \text{putt} && \text{trip} \\ & \text{pip} && \text{putty} && \text{triton} \\ & \text{pit} && \text{riot} && \text{troop}\\ & \text{piton} && \text{rip} && \text{trot} \\ & \text{pity} && \text{root} && \text{trout} \\ & \text{poi} && \text{rooty} && \text{try}\\ & \text{point} && \text{ropy} && \text{tryout} \end{align*}

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