a belief (or system of beliefs) accepted as authoritative by some group or school
"The ancient Stoics held that living in accordance with nature was the only true philosophy for achieving inner peace."
the rational investigation of questions about existence and knowledge and ethics
"After years of studying history, she decided to pursue a degree in philosophy to formally explore deep questions about human nature and morality."
any personal belief about how to live or how to deal with a situation
"self-indulgence was his only philosophy"
"my father's philosophy of child-rearing was to let mother do it"
The love of wisdom.
"After years of studying ancient texts, she realized that her lifelong pursuit was truly a philosophy in the original sense of loving wisdom rather than just accumulating facts."
In plain English: Philosophy is the study of big questions about life, knowledge, and what is right or wrong.
"She taught her children to live by a simple philosophy of kindness and honesty."
Usage: Use "philosophy" to describe a specific branch of knowledge or a particular system of beliefs about life and existence, rather than referring to the abstract concept of loving wisdom itself. When discussing a person's general outlook on life, it is often clearer to say they have "a philosophy" regarding a topic instead of using the term loosely as a synonym for thoughts or opinions.
To philosophize.
"After watching the storm roll in, he spent an hour just standing on the porch and philosophizing about nature's indifference to human plans."
In plain English: To philosophize means to think deeply about important questions and ideas.
"The wise teacher taught his students to philosophy by asking them deep questions about life and truth."
Usage: Philosophy is not used as a verb; instead, use the word philosophize when you mean to think deeply about fundamental questions or to view situations with a detached, reflective attitude. Do not say "he philosophyed" or "she philosophy about life."
The word philosophy comes from the Ancient Greek phrase meaning "love of wisdom," which was adopted into Latin and then French before entering Middle English. It replaced an older Germanic term for the same concept, bringing with it a focus on the pursuit of knowledge rather than just practical skill.