singular and plural nouns

Kindly clarify the following nouns are singular or plural (is or are)-

Alumni/Alumnus
Bacteria/Bacterium
Criteria/Criterion - What is the criteria?? What are the criteia??
Formulae/Formula
Media - Media is...?? Media are...??
Phenomenon/Phenomena
Glasses - The glasses you are wearing is dirty?? are dirty??
Means
Scissors
Statistics