General Meaning: Ten
* decade: a period of ten years
* decimal: relating to or based on the number ten
* decimeter: a unit of length equal to one-tenth of a meter
* deciliter: a unit of volume equal to one-tenth of a liter
* decigram: a unit of mass equal to one-tenth of a gram
* decilitre: a unit of volume equal to one-tenth of a litre
Other Meanings
* decamp: to leave a place secretly or suddenly
* decent: conforming to standards of morality or propriety
* deception: the act of misleading someone
* decide: to make a choice or judgment
* decay: to rot or decompose
* decrease: to become smaller or less
* decorate: to make something more attractive
* deduce: to reach a conclusion by reasoning
* dedicate: to devote something to a particular purpose
* defeat: to overcome or beat in a competition
* defend: to protect someone or something from attack
* defer: to postpone something or delay
* defiance: open resistance to an order or demand
* define: to explain the meaning of a word or concept
* deficit: a shortage or shortfall
* degree: a unit of measurement for angles or temperature
* dehydrate: to remove water from something
* deject: to make someone sad or disheartened
* delay: to postpone something or make it happen later
* delete: to remove something, especially from a computer file
* deliver: to bring something to a person or place
* demand: to ask for something forcefully
* demolish: to destroy something completely
* demonstrate: to show or prove something
* denote: to indicate or represent something
* deny: to refuse to admit something
* depart: to leave a place
* depend: to rely on someone or something
* depress: to make someone sad or disheartened
* derive: to obtain something from a source
* describe: to give an account of something
* desert: to abandon someone or something
* design: to plan or create something
* desire: to want something very much
* despair: a feeling of complete hopelessness
* destroy: to damage something beyond repair
* detach: to separate something from something else
* determine: to find out or decide something
* develop: to grow or progress
* device: a piece of equipment or tool
* devote: to give something to a particular purpose
* diagnose: to identify the cause of a problem
* dictate: to give orders or instructions
* differ: to be different from something else
* diffuse: to spread something out
* digest: to break down food in the stomach
* digitize: to convert information into a digital format
* diminish: to make something smaller or less
* direct: to guide someone or something
* disappear: to vanish or become invisible
* disclose: to reveal something that was secret
* discover: to find something new or unexpected
* discuss: to talk about something with someone
* disease: an illness
* disguise: to change someone's appearance to hide their identity
* dismantle: to take something apart
* disobey: to refuse to follow an order
* dispose: to get rid of something
* dispute: to argue with someone about something
* dissolve: to break down or disappear
* distance: the space between two points
* distinct: clearly different from other things
* distract: to take someone's attention away from something
* distribute: to give something to people or places
* divide: to separate something into parts
* divine: relating to God or gods
* document: to record something in writing
* dominate: to have control over something
* donate: to give something to a charity
* dormant: inactive or sleeping
* doubt: to question something
* downward: in a downward direction
* draft: to make a rough version of something
* drain: to remove liquid from something
* draw: to make a picture or sketch
* dream: to have thoughts or images while sleeping
* dress: to put on clothes
* drive: to control a vehicle
* drop: to fall or let something fall
* drown: to die by being underwater
* due: owed or expected
* duplicate: to make an exact copy of something
* during: within a particular period of time
* dwell: to live in a place
* dye: to change the color of something
This is not an exhaustive list, but it provides a good starting point for understanding the prefix "dec" and its many meanings.