Definition: A type of needle-shaped crystal found in some plant cells, often made of calcium oxalate, that can occur in bundles.

Example: The raphides in the plant's cells help deter herbivores by causing irritation.

Definition: A type of needle-like crystal found in some plants, often made of calcium oxalate, or a needle-shaped structure in sponges.

Example: The raphis crystals in the plant cells help to provide structural support.

Definition: Moving or happening very quickly.

Example: The rapid growth of technology has changed our lives significantly.

Definition: A fast-moving section of a river where the water flows quickly, often with obstacles that create rough surfaces.

Example: The kayakers navigated through the rapids with skill and excitement.

Definition: A type of bird that hunts and feeds on other animals, or a small to medium-sized predatory dinosaur known for its sharp claws and agility.

Example: The raptor soared high in the sky, searching for its next meal.

Definition: Describing animals, especially birds, that are adapted to catch and eat other animals.

Example: The eagle is a raptorial bird known for its sharp talons and keen eyesight.

Definition: Not often found or seen; unusual or uncommon.

Example: Finding a four-leaf clover is a rare occurrence.

Definition: A decrease in density and pressure in a medium, often related to sound waves, where the particles are spread apart.

Example: The rarefaction of air allows sound waves to travel more easily in certain conditions.

Definition: The quality or state of being uncommon or not often found.

Example: The rareness of the species makes it a target for conservation efforts.

Definition: Describing something that is maturing or becoming ready to eat earlier than usual.

Example: The rareripe fruit was ready to be picked weeks before the others.

Definition: A type of fruit or vegetable that matures and becomes ready to eat sooner than others of its kind.

Example: The rareripe tomatoes were ready for harvest weeks before the others.

Definition: The least common or most unusual; something that is not often found or seen.

Example: The rarest species of bird in the world is critically endangered.