Here is a good list of irregular plurals that everyone faces in academic texts:

Singular (-is) | Plural (-es)

Analysis -> Analyses = Анализ -> Анализы
Axis -> Axes = Ось -> Оси
Crisis -> Crises = Кризис -> Кризисы
Diagnosis -> Diagnoses = Диагноз -> Диагнозы
Prognosis -> Prognoses = Прогноз -> Прогнозы

Singular (-um) | Plural (-a)

Datum -> Data = Данная -> Данные
Memorandum -> Memoranda = Заметка -> Заметки
Bacterium -> Bacteria = Бактерия -> Бактерии
Stratum -> Strata = Слой -> Слои
Curriculum -> Curricula = Обучение -> Обучения

Singular (-us) | Plural (-i)

Fungus -> Fungi = Гриб -> Грибы
Nucleus -> Nuclei = Ядро -> Ядра
Alumnus -> Alumni = Выпускник -> Выпускники
Syllabus -> Syllabi = План (лекции)-> Планы (лекций)

Singular (-on) | Plural (-a)

Criterion -> Criteria = Критерия -> Критерии


Also, keep in mind the difference between man and men; woman and women. When you find yourself stuck on the exam, contemplating (созерцать) on the matter, recall Spiderman, and you’ll be able to quickly distinguish the two nouns.