Definition: Something that is very important and necessary for something else to happen or succeed.

Example: The scientist played a pivotal role in the discovery of the new vaccine.

Definition: In a way that is crucial or essential to the outcome of something.

Example: The decision pivotally influenced the direction of the project.

Definition: A substance that has no therapeutic effect, often used in experiments to test the effectiveness of a real drug by comparing results.

Example: The doctor gave her a placebo to see if her symptoms would improve without actual medication.

Definition: An organ in female mammals that forms during pregnancy, connecting the mother to the developing fetus and providing nutrients and oxygen through the umbilical cord.

Example: The doctor explained how the placenta nourishes the baby during pregnancy.

Definition: Relating to or having a placenta, which is an organ that develops in the uterus during pregnancy to provide nutrients and oxygen to a developing baby.

Example: Humans are classified as placental mammals because they give birth to live young that are nourished before birth through a placenta.

Definition: A type of mammal that gives birth to live young that have developed inside the mother's body, connected to her by a special organ called the placenta.

Example: Humans are classified as placental mammals because they give birth to fully developed babies.

Definition: The process or arrangement of how a placenta forms and attaches in the uterus or within a plant ovary.

Example: The study of placentation is important for understanding both plant reproduction and human pregnancy.

Definition: An extinct type of fish that lived during the Silurian and Devonian periods, known for having bony plates that protected its head and sides, as well as having jaws and fins.

Example: Scientists have discovered fossils of placoderms that show their unique armored bodies.

Definition: Describing a type of scale that is flat and tooth-like, typically found on certain fish like sharks and rays.

Example: The shark's skin is covered in placoid scales that help reduce drag in the water.

Definition: A type of mineral that is part of a group of feldspar minerals, commonly found in many types of rocks, and made up of sodium and calcium aluminum silicates.

Example: Plagioclase is often used in geology to identify different types of igneous rocks.

Definition: A serious disease that can spread quickly and cause many deaths, or a situation that causes a lot of trouble or annoyance.

Example: The city faced a plague that affected thousands of people.

Definition: To cause someone to suffer from a disease or to annoy someone repeatedly.

Example: The constant noise from the construction site plagued the residents for months.