Biological process

down regulation of CD4-positive, alpha beta T cell differentiation, down-regulation of CD4-positive, alpha beta T cell differentiation, downregulation of CD4-positive, alpha beta T cell differentiation, negative regulation of CD4-positive T-cell differentiation, negative regulation of CD4-positive T-lymphocyte differentiation, negative regulation of CD4-positive, alpha beta T lymphocyte differentiation, negative regulation of CD4-positive, alpha beta T-cell differentiation, negative regulation of CD4-positive, alpha beta T-lymphocyte differentiation

Any process that stops, prevents, or reduces the frequency, rate, or extent of CD4-positive, alpha-beta T cell differentiation.

negative regulation of CD4-positive, alpha beta T cell development

Note that immunologists typically use the word 'development' to refer to cells of B or T cell lineages undergoing the process that GO describes as 'cell differentiation'.