Spell components are one of those rules that a lot of tables quietly ignore until the exact moment somebody gets tied up, silenced, disarmed, or otherwise inconvenienced and suddenly everyone wants to know whether the wizard can still cast Fireball.
Most spells have some combination of Verbal, Somatic, and Material components, usually shortened to V, S, and M in the spell description.
If a spell requires a component and you cannot provide it, you cannot cast the spell. That is really the whole foundation of the rule.
The details are where people start arguing, though.
Verbal components are the easiest to understand. If a spell has a V next to it, you need to speak the magical words out loud in a normal speaking voice.
That means you cannot cast it if you are gagged, inside Silence, or otherwise unable to speak properly.
Whispering the spell under your breath because you do not want the guard standing five feet away to notice is also not really what the rule describes. The words are supposed to be spoken audibly, which is important because spellcasting is generally not a subtle activity unless a feature specifically allows you to make it subtle.
This is also why the Sorcerer’s Subtle Spell metamagic is actually useful. If everyone could just mumble Suggestion into their sleeve without anyone noticing, removing the Verbal and Somatic components would not mean much.
Somatic components are the hand gestures.
If a spell requires an S component, you need at least one free hand to perform whatever dramatic finger movements, arcane gestures, or aggressive pointing the spell requires.
And yes, this means what you are holding can matter.
If your wizard has a sword in one hand and a shield in the other, and the spell requires a Somatic component, you may have a problem unless one of those hands can legally be used for the spell.
That said, this is also where Material components come in and make the hand rules a little stranger than you would probably expect.
Material components are the physical things listed in the spell description. Sometimes these are serious things like diamonds. Sometimes D&D decides your powerful arcane ritual requires a tiny ball of bat guano, because apparently wizard school involved a lot more scavenging than anyone mentioned.
For most normal Material components, you do not actually need to carry around every individual piece of nonsense listed in every spell.
A component pouch can provide the required materials, or you can usually use an appropriate Spellcasting Focus if your class allows it.
So, if a spell asks for a feather, a bit of fleece, some sulfur, or another component without a listed price, you normally do not need to keep an Excel spreadsheet of wizard garbage in your backpack.
The important exceptions are components that have a specific cost or are consumed by the spell.
If a spell requires a diamond worth 300 GP, your Spellcasting Focus cannot replace it. You need the actual diamond.
Likewise, if the spell says the component is consumed, you lose it when the spell is cast and need another one next time.
This matters with spells such as Revivify, because the 300 GP diamonds are not flavor text. You cannot wave your arcane focus over the dead fighter and explain that your fancy stick is basically worth the same thing spiritually.
You need the diamonds.
Now, the slightly annoying hand interaction.
If a spell has both Somatic and Material components, the same hand can handle both. You can hold or access the Material component with one hand and use that same hand to perform the Somatic gestures.
However, if the spell has a Somatic component but no Material component, the hand holding your Spellcasting Focus does not automatically solve the problem. You still need a hand free to perform the Somatic component unless another rule or feature allows otherwise.
This distinction sounds incredibly petty until somebody is standing there with a weapon and shield trying to cast something, and then suddenly it becomes the most important rule in the game.
A cleric is a good example. If their shield bears their Holy Symbol and the spell requires Material and Somatic components, the shield can serve as the focus and that same hand can perform the Somatic component.
On the other hand, if the spell requires Somatic components but no Material component, they may need to free a hand first.
Yes, it is weird. Yes, people forget it constantly. No, I would not blame a DM for deciding they do not want to track every hand movement in every fight, but that is the actual rule.
The other thing worth keeping in mind is that components are not just decorative spell descriptions. They are part of how spells interact with the world.
A Verbal component means magical silence matters. A Somatic component means being restrained in a way that prevents hand movement might matter. A Material component means losing your focus or pouch can matter.
That gives the DM tools to create situations where spellcasters cannot simply solve every problem by reading down their spell list.
Regardless of how strictly you want to enforce components at your table, though, I think the important part is consistency. If you normally ignore whether the wizard has a free hand, suddenly remembering the rule when they are about to save the party is going to feel cheap.
So, the basic rule is this. Verbal means you need to speak. Somatic means you need a hand for the gestures. Material means you need the listed component, a component pouch, or an appropriate Spellcasting Focus. Costly or consumed materials usually cannot be replaced by the focus.
And if your wizard actually has every individual spell component carefully written into their inventory, leave them alone. They have suffered enough.
