Definition of heterochromatin in English:
 heterochromatin
noun ˌhɛtərəʊˈkrəʊmətɪnˌhedərōˈkrōmədin
mass nounBiology Chromosome material of different density from normal (usually greater), in which the activity of the genes is modified or suppressed.
Compare with euchromatin
 Example sentencesExamples
-  The organization of DNA into euchromatin and heterochromatin is implicated in gene silencing.
 -  Numerous genes act to remodel and repress chromatin in heterochromatin and around euchromatic genes during development.
 -  Studies of genes translocated to heterochromatin have provided insight into the factors that control chromatin states.
 -  Thus, the density of genes in heterochromatin is about 1% of that in euchromatin.
 -  Genes located in heterochromatin are transcriptionally silenced, irrespective of their own promoter sequences.