January

Jan‧u‧a‧ry /ˈdʒænjuəri, -njʊri $ -njueri/ BrE AmE noun (plural Januaries) [uncountable and countable] (written abbreviation Jan.)
[Date: 1200-1300; Language: Latin; Origin: Januarius, from Janus ancient Roman god of doors, gates, and new beginnings]
the first month of the year, between December and February
next/last January
I haven’t heard from him since last January.
in January
She started working there in January.
on January 6th
Rosie’s party was on January 6th.
on 6th January British English:
He took office on 6th January 1999.
January 6 American English:
The package arrived January 6.

Oxford Advanced Learner's Dictionary

January

Janu·ary [January Januaries] [ˈdʒænjuəri] [ˈdʒænjueri] noun uncountable, countable (abbr. Jan.)
the 1st month of the year, between December and February. To see how January is used, look at the examples at April.
Word Origin:

Old English, from Latin Januarius (mensis) ‘(month) of Janus ’, the Roman god who presided over doors and beginnings.

Cambridge Advanced Learner's Dictionary

Cambridge Advanced Learner's Dictionary - 4th Edition

January / ˈdʒæn.jʊ.ri / / -juː.er.i / noun [ C or U ] ( written abbreviation Jan. )

A1 the first month of the year, after December and before February:

Her father died in January.

His birthday is 25 January .

We're going skiing next January.

Collins COBUILD Advanced Learner’s English Dictionary

January

[ʤæ̱njəri, AM -jueri]
♦
Januaries
N-VAR
January is the first month of the year in the Western calendar.
  We always have snow in January...
  She was born on January 6, 1946...
  I haven't seen my own daughter since last January.

Merriam-Webster's Advanced Learner's Dictionary

Merriam-Webster's Advanced Learner's Dictionary:

January

Jan·u·ary /ˈʤænjəˌweri/ noun, pl -ar·ies : the first month of the year

[noncount]

• in (early/middle/mid-/late) January
• early/late in January
• They arrived on January the fourth. = (US) They arrived on January fourth. = They arrived on the fourth of January.

[count]

• Sales are up (for) this January in comparison with the previous two Januaries.
- abbr. Jan.;

January

noun