What is the difference between the following words? write their definitions. 1) gain and raise 2) tremble and flicker

Gain is the process of adding to a person vitality, energy and new powerful resources (one of the meanings)
Raise is up, rise, rise, increase, increase, multiplication, improvement
Tremble is frequent convulsive muscle contraction
Flicker is cosmic radiation sources, the observed irregular change in the radiation intensity of cosmic bodies 
Очень неоднозначное задание. Разницы почти нет. Написал бы на русском, у этих слов много значений) А так удачи!