http://www.enotes.com/history/q-and-a/what-were-causes-dust-bowl-1930s-35681 Well, the Great Depression of the 1930s was one of the main factors that caused the Dust Bowl of the same period but it was not the MAIN CONTRIBUTING factor that lead to the ecological disaster.
The definition of a suffix is a letter, syllable or group of syllables that are added to the end of a word to change it into something else. An example of suffix is adding cycle to motor which creates motorcycle.
It's a first-declension feminine noun. The-tia, -tiae suffix is first-declension, and it creates abstract nouns. It's seen widely in Latin and is worth memorizing as such. This word amicitia is often used in the ablative of manner, that is, cum amicitiÄ, meaning with friendship or in a friendly way..