The research focuses on the relationship between matters of sentence formation and use of appropriate vocabulary and the writ ing composition levels among students in Suawan High School. They have regard to the structural formation of sentences as the bas is of sound conventions in writing professional work. The previous literature shows that impairments in the formation of individual sentences correlate troubles in creation of coherent and properly structured texts due to syntactic and grammatical deficit (Berninger et al., 2010). Just as writing composition involves not only having a facility with language to create sentences but also with the language to stitch the paragraphs together, an area that can be learned with explicit instruction (Limpo & Alves, 2013). Another vital area of learning that is regarded important in writing composition is vocabulary. The variation in the quality of their writing most centrally has to do with the fact that a rich vocabulary helps students express what they have to say in a creative manner. Research has also shown that an increase in the student’s developed word vocabulary leads to an increased number of developed better forme d sentences within any piece of work done; thus, enhancing the general quality of writing (Oktaviani et al., 2021). In addition, the study conducted by Ekinci & Ekinci (2021) showed an increase in students’ vocabulary knowledge which helped the students’ writing greatly if there was an online vocabulary instruction. Such results imply that vocabulary learning cannot be restricted to memorization but also encompasses knowledge about word usage in strings. The research will describe how vocabulary and sentence structure work hand in hand in writing by evaluating various elements of writing. Studies show a positive correlation between students’ composing descriptive text and the students’ mastery of the sente nce and words (Oktaviani et al., 2021). This relationship implies the need for handling instructional relations between the structure of a sentence and vocabulary development. Briceño (2015) backs the notion that explicit instructional approach, including language-oriented conversations and shared-reading approaches, may help students to develop an understanding of the architectural/founding structures of sentences in Relatively syntactic/grammatical languages. Working memory, as well as other processes relevant to language acquisition, are also considered to contribute to the development of writing skills. Berninger et al. (2010) indicating that poor writing may be due to those cognitive areas leading to poor use of all aspects of syntax and vocabulary. Hence, one must take account of certain cognitive factors when designing learning-teaching approaches for enhancing students’ writing performance. In summary, sentence structure mastery and vocabulary knowledge are interconnected elements that significantly influence students' writing composition skills. Instructional strategies that integrate the teaching of vocabulary and sentence structure can enhance students' abilities to produce clear and coherent compositions.