| indefatigable(adjective, strong, firm, determined, steady) |
| insistent(adjective, demanding) |
| interminate(adjective, persistent, continuous, endless, infinite) |
| intermittent(adjective, regular, normal, continuous, everlasting) |
| level(adjective, continuous) |
| livelong(adjective, durable) |
| long(adjective, endless, durable, ceaseless) |
| ongoing(adjective, continue, constant, continuous, permanent) |
| perdurable(absolute, continuous, endless, immense, permanent) |
| persisting(adjective, determined, steady, stable, persistent) |
| prolonged(adjective, durable) |
| reappearing |
| redundant(adjective, regular, normal, repetition, recurrent) |
| returning |
| sequential(adjective, order, continuous) |
| smooth(continuous, flowing, operating) |
| thick(adjective, regular, normal, frequency, recurrent) |
| tireless(adjective, strong, firm, determined, active) |
| ubiquitous(regular, normal, recurrent) |
| unchangeable(adjective, continuous) |