In legalese, there are distinctions. Canon law (which determined the legalese in most western languages) considers a cult to be a subset with specific laws and customs (e.g. the “Oriental Catholic” rites), but at still part of the normative religion. By that standard, Ashkenazim and Sefardim would be “cults” of Judaism.
In some modern legal systems, a “cult” may be defined such as to allow its persecution even though “religion” is respected (consider “Scientology” which is banned is some countries that otherwise hold by freedom of religion). From a Jewish perspective, “Reform” would be probably considered a “cult”, as would be Christianity and Islam.
In popular American usage, a “cult” is a religion that you disrespect.
A factor to consider is whether members of the groups in question freely intermarry without asking one party to convert. That in part gets to the definition of a sect.