The study analysed the Morpho-Syntactic Errors in Written English of Form Three Secondary
School Students in Langata Sub-County, Nairobi County. The studys main goal was to
analyse number agreement and punctuation mark errors made by students. The objectives were
to identify the common morpho-syntactic errors in students written English, the frequency of the
errors in the students written English, and the possible causes of these errors. The study made
use of Corders theory of Error Analysis (1967 and 1974). A sample of a hundred students
written compositions was collected from all the Langata Sub-County form three public
secondary school students from a single written composition. The errors were determined
through a consideration of the deviations in students grammar from the norms of the target
language (British English). Data were first presented in tables and finally, percentages of the
frequency of these errors were tabulated. The following morpho-syntactic errors in number
agreement and punctuation marks were discovered after analysis of the written composition:
noun phrase agreement errors, singular subjects with plural verb errors, plural subjects with
singular verb errors, missing comma errors, lack of full stops at the end of sentences, and, misuse
of semicolons. The findings showed that noun-agreement errors 55%, singular subjects with
plural verb errors 63%, plural subjects with singular verb errors 56%, and comma-missing errors
61% were frequent in the students written compositions. Finally, based on the available
literature on error analysis, the study discussed the possible causes of the errors observed. It
emerged that omission, overgeneralization, incomplete application of the rules, and inadequate
understanding of the rules, were the main causes of these errors. Based on the results of the
current study, the study recommended that teachers of English should emphasize morphosyntactic rules, encourage learners to read English texts of various genres, emphasize the
importance of all punctuation marks, and lastly, both teachers and students should communicate
using target language frequently in the classroom.