Nonlinear phenomena are phenomena, which, in contrast to a linear system, cannot be explained by a mathematical relationship of proportionality (that is, a linear relationship between two variables).

Lea Uradu, J.D., is a Maryland state registered tax preparer, state-certified notary public, certified VITA tax preparer, IRS annual filing season program participant, and tax writer. Vikki Velasquez ...

Julia Kagan is a financial/consumer journalist and former senior editor, personal finance, of Investopedia. Toby Walters is a financial writer, investor, and lifelong learner. He has a passion for ...