optical illusion   1402 |

.optical il lusion noun something that tricks your eyes and makes you think that you can see sth that is not there, or makes you see sth as different from what it really is        —picture on previous

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op-ti-cian /Dp'tijn; NAmE a:p-/ noun 1 (also oph­thalmic optician) (both BrE) (also op-tom-etrist NAmE, BrE) a person whose job is to examine people’s eyes and to recommend and sell glasses Bill ]§[;    2 opti­

cian’s {pi. op-ti-cians) the shop/store where an optician works IM /£: to go to the optician’s A BS ^ 3 a person who makes lenses, glasses, etc. op-tics /'Dptiks; NAmE 'a:p-/ noun [U] the scientific study of sight and light — see also fibre optics op ti mal /'optimal; NAmE'aip-/ adj. = optimum(I) op ti mism /’nptimizam; NAmE 'a:p-/ noun [U] ~ (about/ for sth) a feeling that good things will happen and that sth will be successful; the tendency to have this feeling 7*1;          optimism about/for the future AX

(ft 7 *1 o We may now look forward with optimism. fSffRSFE  AXo 0 a mood of cautious

optimism ii fit 7*1 (ft 7 j# 0 There are very real grounds for optimism. (ftfifcWS^Wl^MRlo E133 pessimism op ti mist /'optimist; NAmE 'a:p-/ noun a person who always expects good things to happen or things to be successful 7*l(ftA; 7Xiii EH3 pessimist op-ti-mis tic /.nptTmistik; NAmE ,a:p-/ adj. ~ (about sth)

| ~ (that ... ) expecting good things to happen or sth to be successful; showing this feeling 7*l(ft; jfe7*&#'A (ft H771 positive : She’s not very optimistic about the outcome of the talks. M*^7‘$(ft£Rft7:A7*lo 0 They are cautiously optimistic that the reforms will take place. M 1 Ft ^ Ft $ ¥ ^      Ift 7*1 c 0 We are now

taking a more optimistic view. %%\UMfEtWl£7*l.#J#

0 o in an optimistic mood W 7 *1 (tfJ 'If       o I think

you’re being a little over-optimistic. $cfif 7*17o 033 pessimistic ► op ti mistic al ly /-kli/ adv. op ti mize {BrE also -ise) /’nptimaiz; NAmE ’a:p-/ verb [VN] to make sth as good as it can be; to use sth in the best possible way {^ftftffc;      : to optimize the

use of resources

op ti mum /'nptimam; NAmE ’a:p-/ adj. [only before noun] 1 (also op-ti-mal) the best possible; producing the best possible results ft fi (ft; ft it H (ft: optimum growth ft o the optimum use of resources Ft!£i®£ft;£7f![Jl

0                  the optimum conditions for effective learning {7uE7FJ ^ftlftftfiA# 2 the optimum noun [sing.] the best possible result, set of conditions, etc. ftfi^ft; ft£f (ft 7# EQ0 ideal

op tion 0-w /■ Dpjn; NAmE 'a:p-/ noun

1                  [C, U] ~ (of doing sth) | ~ (to do sth) something that you can choose to have or do; the freedom to choose what you do of3^j?(ftft#/; )4ft; i4#ft;

^ : As I see it, we have two options ... ?cCIW

W#j4#-- 0 There are various options open to you. jfo W ^ # t& # o O Going to college was not an option for me.       o I had no option

but to {= I had to) ask him to leave. ffc #ij ft 14 #, R W i# ilk M 7 o 0 Students have the option of studying abroad in their second year. #X7:27ftN‘lTIMi4#LB IS ^ o 0 A savings plan that gives you the option to vary your monthly payments. —         llEBWtfclft

0 This particular model comes with a wide range of options (= things you can choose to have when buying sth but which you will have to pay extra for).

o 2 [c] a subject that a student can choose to study, but that they do not have to do 14 [it if<: The course offers options in design and computing.       7        „

3 [C] ~ (ojj sth) | - (to do sth) the right to buy or sell sth at some time in the future ( AX(ft )      We

have an option on the house.    o

The property is for rent with an option to buy at any time. 7 fcB ffl., FPJftlFf XT 0 0 He has promised me first option on his car (= the opportunity to buy it before anyone else).        o

share options (= the right to buy shares in a company) 4 [C] (computing if) one of the choices you can make when using a computer program 14 tiR ;

#: Choose the ‘Cut’ option from the Edit menu. |$| j4¥Xj4      mo itSTm keep/leave your ‘options

open to avoid making a decision now so that you still have a choice in the future the

.soft/,easy ‘option (often disapproving) a choice which is thought to be easier because it involves less effort, difficulty, etc. $£ft(fti4#; FIS: They are anxious that the new course should not be seen as a soft option. jMl 0 He decided to take the easy option and give them what they wanted, ftk 7m&,

op tion al /'opjanl; NAmE 'a:p-/ adj. that you can choose to do or have if you want to rT 14#(ft; )4#(ft: Certain courses are compulsory, others are optional. X ® i$. ft IkilMiKft, 7 lib 14 H (ft o 0 This model comes with a number of optional extras (= things you can choose to have but which you will have to pay extra for). 14 — M

mm.

op-tom-etrist /Dp'tnmatrist; NAmE a:p'ta:m-/ noun = optician(I)

op-tom-etry /np'tnmatri; NAmE a:p'ta:m-/ noun [U] the job of measuring how well people can see and checking their eyes for disease tlAil'J/E 'opt-out noun (often used as an adjective 1$

1 (in Britain) the action of a school or hospital that decides to manage its own money and is therefore no longer controlled by a local authority or similar organization (       $*(ft )

iM f±J,         2 the act of choosing not to be involved in

an agreement 7#J=3$)‘iSl(ft$:AE: an opt-out clause li tB (ft ^ Dt O MPs hoped to reverse Britain’s opt-out from the treaty.

opu lent /'npjalant; NAmE 'a:p-/ adj. {formal) 1 made or decorated using expensive materials ^6*£(ft;

(ft; i£]|j§ (ft H771 luxurious 2 (of people A) extremely rich ft U W (ft ; fif H   wealthy ► opu-lence

/-Ians/ noun [U] opu-lent-ly adv. opus /'aupas; NAmE 'ou-/ noun {pi. opera /'npara; NAmE 'a:p-/) [usually sing.] 1 {abbr. op.) a piece of music written by a famous composer and usually followed by a number that shows when it was written (         ft

fBeethoven’s Opus 18     ^ % 7 A n” 2 {formal) an important

piece of literature, etc., especially one that is on a large scale 1X^4 )    ) Aft,  H33

work — see also magnum opus Or 0-w /o:(r)/ conj.

2                  used to introduce another possibility ( ^ W 31 fB R —

# Rf tb'14 ) ^ , ^ # , £E A : Is your sister older or younger than you? ^(ft          Sli/h ? 0 Are you

coming or not?     0 Is it a boy or a girl? &

'f'M&iEMiafZ? 0 It can be black, white or grey, t: nj li Ji H (ft , g #J M M. 6^1 o — compare either adv. (3)

3                  used in negative sentences when mentioning two or

more things (         ) &

7: He can’t read or write.         0 There

are people without homes, jobs or family. 7f A ft M, XAXfF,    — compare neither adv.{2)

4                  (also or else) used to warn or advise sb that sth bad could happen; otherwise ( Iff oI&b ) 51, 7 M: Turn the heat down or it’ll burn. AJFX—

7 o 4 used between two numbers to show approximately how many ( #77 W 7          7 AIh] A 7 ^

^ g ) A^tf: There were six or seven of us there.

Wan, ttAftlo 5 used to introduce a word or phrase that explains or means the same as another ( hi 7 31 tB I? W-14   ^ # i&: geology, or the science of

the earth’s crust    ^#i&i&TB(ftf47 0 It weighs a

kilo, or just over two pounds.   ^ ® fi ~■ 7 7, a5cWi^.

WW£ — .g.JLo 6 used to say why sth must be true ( ffl7MJKH ) FI, 7M'J: He must like her, or he wouldn’t keep calling her. ~XH- fKM tnh&tl X iS o 7 used to introduce a contrasting idea (rffi 7 5ft 1£ fft'HE &") : He was lying—or was he? fife X ift it, tS Ji ft W it ? fHTOI or so about A :