ABSTRACTrnThis Thesis is entitled “A STUDY ON THE ABILITY IN USING INDEFINITErnPRONOUNS IN ENGLISH SENTENCES OF THE ELEVENTH GRADE STUDENTS OFrnSMKN 2 KUPANG IN SCHOOL YEAR 2012/2013”. This study was conducted in order tornanswer the following questions: (1) Are the eleventh grade students of SMKN 2 Kupang able tornuse Indefinite Pronouns in English Sentence? (2) What is the students’ level of ability in usingrnIndefinite Pronouns in English Sentence? And (3) What are the difficulties faced by the studentsrnof SMKN 2 Kupang in using Indefinite Pronouns in English Sentences? The main objectives ofrnthis study are : (1)To find out whether the eleventh grade students of SMKN 2 Kupang are ablernto use Indefinite Pronouns in English Sentences correctly. (2) To find out their level of ability tornuse Indefinite Pronouns in English sentence. (3) To know the difficulties in using IndefiniternPronouns in English Sentences. In this study the writer used descriptive method in order tornanalyze and describe the ability level of eleventh grade of SMKN 2 Kupang in the school yearrn2012-2013 In Using Singular Indefinite Pronouns in English Sentences.The respondents of thisrnstudy were 40 students. The instrument that the writer used for gathering the data was the test.rnThe test consisted of (40) test items, divided into two types namely: 20 test items were multiplernchoice and (20) test items were Underline the Correct Answer in the Brackets. The result of therndata analysis shows that (1) The eleventh grade students of SMKN 2 Kupang are able to usernSingular Indefinite Pronounce in English Sentences. (2).The ability level of eleventh grade ofrnSMKN 2 Kupang was” AVERAGE” (61.13), (3) and the difficultiess faced by students (1)rnDifficulties to differentiate, three patterns namely; Singular Indefinite Pronouns, PluralrnIndefinite Pronouns, and Singular or Plural Indefinite Pronouns, in answering test especiallyrnMultiple Choices test and Underlining Test. And (2) They don’t know how to determine SingularrnIndefinite Pronouns in three terms namely: The use of Affirmative e.g. (There is......in your hair. Irnthink it is a bug) Interrogative e.g. (Does…….have pencil I can borrow?) and Negative e.g. ((Herndidn’t say......useful. All were nonsense).The write would like to suggest to (1)The Teacherrnshould teach the students how to use singular indefinite pronouns, plural indefinite pronouns andrnsingular or plural indefinite pronouns specially constructing the sentences, and how torndifferentiate the use of singular indefinite pronouns plural indefinite pronouns and singular orrnplural indefinite pronouns in affirmative, negative and interrogative sentences.(2)The studentsrnshould do more exercise and learn about the singular indefinite pronouns specially which to usernin affirmative, negative and interrogative in sentences, and the students also emphasize torndifferentiate the singular indefinite pronouns, plural indefinite pronouns and singular indefinite