Comprehensive Guide to Spanish Numbers and Hundreds

Foundations: Digits and Tens (0 to 99)

• Base Digits (0–9):

  • $0 = \text{cero}$
  • $1 = \text{uno}$
  • $2 = \text{dos}$
  • $3 = \text{tres}$
  • $4 = \text{cuatro}$
  • $5 = \text{cinco}$
  • $6 = \text{seis}$
  • $7 = \text{siete}$
  • $8 = \text{ocho}$
  • $9 = \text{nueve}$

• Teens (10–19):

  • $10 = \text{diez}$
  • $11 = \text{once}$
  • $12 = \text{doce}$
  • $13 = \text{trece}$
  • $14 = \text{catorce}$
  • $15 = \text{quince}$
  • $16 = \text{dieciséis}$
  • $17 = \text{diecisiete}$
  • $18 = \text{dieciocho}$
  • $19 = \text{diecinueve}$

• Twenties (20–29):

  • Written as a single combined word using the prefix veinti-
  • $20 = \text{veinte}$
  • $21 = \text{veintiuno}$
  • $22 = \text{veintidós}$
  • $23 = \text{veintitrés}$
  • $24 = \text{veinticuatro}$
  • $25 = \text{veinticinco}$
  • $26 = \text{veintiséis}$
  • $27 = \text{veintisiete}$
  • $28 = \text{veintiocho}$
  • $29 = \text{veintinueve}$

• Tens (30–90):

  • Written as separate words connected by the conjunction y when preceding a unit digit
  • $30 = \text{treinta}$
  • $40 = \text{cuarenta}$
  • $50 = \text{cincuenta}$
  • $60 = \text{sesenta}$
  • $70 = \text{setenta}$
  • $80 = \text{ochenta}$
  • $90 = \text{noventa}$

Detailed Mechanics of the Hundreds (100 to 900)

• Syntax Rules for 100 (cien versus ciento):

  • Use cien when the number is exactly $100$, or when directly modifying a noun or a larger multiplier (e.g., cien libros, cien mil).
  • Use ciento when $100$ is followed by a non-zero tens or units digit to form compound numbers (e.g., $101 = \text{ciento uno}$, $150 = \text{ciento cincuenta}$).

• Complete List of Hundreds (100–900):

  • $100 = \text{cien / ciento}$
  • $200 = \text{doscientos / doscientas}$
  • $300 = \text{trescientos / trescientas}$
  • $400 = \text{cuatrocientos / cuatrocientas}$
  • $500 = \text{quinientos / quinientas}$ (Irregular stem root: quini- instead of cuatro-)
  • $600 = \text{seiscientos / seiscientas}$
  • $700 = \text{setecientos / setecientas}$ (Irregular stem root: sete- instead of siete-)
  • $800 = \text{ochocientos / ochocientas}$
  • $900 = \text{novecientos / novecientas}$ (Irregular stem root: nove- instead of nueve-)

Gender Agreement Rules for Hundreds

• Unlike numbers below $100$ (with the exception of $1 = \text{uno}$ and compound numbers ending in $1$), all hundreds from $200$ through $900$ possess masculine and feminine forms:

  • Masculine endings utilize -os (doscientos, quinientos, novecientos).
  • Feminine endings utilize -as (doscientas, quinientas, novecientas).

• Application Examples:

  • $200\text{ books} = \text{doscientos libros}$ (Masculine plural noun)
  • $500\text{ chairs} = \text{quinientas sillas}$ (Feminine plural noun)
  • $700\text{ pages} = \text{setecientas páginas}$ (Feminine plural noun)
  • $900\text{ cars} = \text{novecientos coches}$ (Masculine plural noun)

Compound Number Construction Rules

• Order of Components:

  • Compound numbers are constructed by stating the hundred value first, followed directly by the tens and unit values.
  • The conjunction y is inserted exclusively between tens and units ($31$ to $99$). Never place y immediately after hundreds.

• Specific Formulas and Examples:

  • Formula for Hundreds + Tens + Units: $\text{Hundred} + \text{Ten} + y + \text{Unit}$
  • $142 = \text{ciento cuarenta y dos}$ (Incorrect form: ciento y cuarenta y dos)
  • $205 = \text{doscientos cinco}$ (Direct combination of hundred and single unit)
  • $578 = \text{quinientos setenta y ocho}$
  • $716 = \text{setecientos dieciséis}$
  • $999 = \text{novecientos noventa y nueve}$

Higher-Order Numbers: Thousands, Millions, and Formatting

• Thousands (Mil):

  • The word mil is an invariant modifier and does not take a plural -es form when counting specific thousands.
  • $1\,000 = \text{mil}$
  • $2\,000 = \text{dos mil}$
  • $5\,000 = \text{cinco mil}$
  • $100\,000 = \text{cien mil}$
  • Gender agreement applies to the hundreds place within thousands: $200\,000\text{ women} = \text{doscientas mil mujeres}$.

• Millions (Millón / Millones):

  • $1\,000\,000 = \text{un millón}$
  • $2\,000\,000 = \text{dos millones}$
  • The noun millón requires the preposition de when immediately followed by a noun: $1\,000\,000\text{ dollars} = \text{un millón de dólares}$, $5\,000\,000\text{ people} = \text{cinco millones de personas}$.
  • If other numerical terms follow the million, de is omitted: $1\,000\,500\text{ dollars} = \text{un millón quinientos dólares}$.

• Numerical Punctuation Standards:

  • In standard international Spanish usage, period and comma functions in numbers are opposite to English conventions.
  • Periods (or spaces) are used as thousands separators: $1.000$ or $1\,000$.
  • Commas are used as decimal points: $3,14$ (pi).