Time is of the essence when it comes to today’s word pair. The more common word period refers to an interval of time that is meaningful because of its particular characteristics. This could be a period of great profitability for a company, for instance, or a period of adjustment, as for an individual when life circumstances change. The noun epoch emphasizes historical significance and is used of a particular period marked or defined by distinctive features or events. If a treaty ushers in an epoch of peace and goodwill, then it marks the beginning of a new period that, in its absence of war and hostility, is distinct from what preceded it. In geologic time, an epoch is a unit of time (shorter than a period) during which a rock series is formed.

The verb remain is used a few different ways. If two countries remain at peace, they are continuing in a peaceful state. If a front wall is all that remains of a fort, that wall is all that is left after the removal, loss, or destruction of the rest of the fort. If you remain at home, you are staying at your abode. To linger is to remain or stay on in a place longer than is usual or expected. The use of this verb implies reluctance to leave. If a few friends linger after a party, it means they continue to hang around for a while after everyone else has left. Linger can also suggest a musing or contemplative quality. If you linger over the beauty of a painting, for instance, you are dwelling in contemplation, thought, or enjoyment.

The noun friend is a broad term that suggests varying degrees of familiarity. It can refer to someone who is on good terms with another (Who goes there? Friend or foe?), to a supporter or patron of some institution (friends of the Boston Symphony), or to a connection on social media. Most commonly, though, a friend is a person with whom one is on intimate terms and for whom one feels a warm affection. This is the meaning that gets us closest to the noun companion. A companion is a person who shares one's activities, fate, or condition. You might have a traveling companion or a companion in despair. The key difference is that a companion is a person who you are frequently in the company of. A friend may be far away, but still hold a special place in your heart.