Regular Expressions 101

Positive Lookbehind(?<=[0-9])

Character Class[0-9]

0-9one character from 0 (48₁₀) to 9 (57₁₀)

\s+any whitespace character, repeated at least once

Positive Lookahead(?=(?:st|[rn]d|th)(?: [^\W\d_]|$))

Non-Capturing Group(?:st|[rn]d|th)

1st Alternativest

stthe literal text st (case sensitive)

2nd Alternative[rn]d

Character Class[rn]

rthe literal r (114₁₀ / 162₈ / 72₁₆) (case sensitive)

nthe literal n (110₁₀ / 156₈ / 6E₁₆) (case sensitive)

dthe literal d (100₁₀ / 144₈ / 64₁₆) (case sensitive)

3rd Alternativeth

ththe literal text th (case sensitive)

Non-Capturing Group(?: [^\W\d_]|$)

1st Alternative [^\W\d_]

the literal (32₁₀ / 40₈ / 20₁₆)

Negated Character Class[^\W\d_]

\Wany non-word character

\da digit

_the literal _ (95₁₀ / 137₈ / 5F₁₆)

2nd Alternative$

$end of line

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

Detailed match information will be displayed here automatically.

25 tokens

Regular Expression

(?<=[0-9])\s+(?=(?:st|[rn]d|th)(?: [^\W\d_]|$))

New

10   th elementary
1  st grade
133  rd anniversary

abc123 th 33333    rddccc
10 thetree
20 street

10   th elementary
1  st grade
133  rd anniversary

abc123 th 33333    rddccc
10 thetree
20 street