The term “used to” is a semi-modal verb in English. Semi-modal verbs, also known as quasi-modal verbs or marginal modal verbs, are a group of verbs that share some features with modal verbs but are not true modals. Unlike modal verbs, semi-modal verbs can be inflected for tense and person, and they can take a form of ‘DO’ as an auxiliary verb in negative and interrogative sentences.
The semi-modal “used to” is typically used to express that an action happened continuously, habitually, or frequently during a period in the past, but not any longer. For example:
“I used to get up early when I lived in New York.”
“She used to live in Ireland.”
“We used to be in a band together.”
“This watch used to belong to my father.”
So, when we speak about a past habit, condition, or fact that is no longer the case, we can use the semi-modal “used to” with the base form of the verb.
Research notes:
This is a tricky grammar structure to locate in a corpus for a number of reasons. The main one is that the claws 7 tagger doesn’t seem to recognise “used” as VMK, a semi modal auxiliary. It does recognise “ought to” but that is much easier for it since the “use” is far more common with more variation. That aside we can without tags do a search for “Noun + used to + infinitve”. We add the noun to avoid the high number of passive constructions: “is used”. So here is our unedited list from iWeb which require manual checking. Note that half of these are elipted relative clauses. As in “The term which is used to describe pain.”
1 TERM USED TO DESCRIBE 8333
2 DRUGS USED TO TREAT 1573
3 MEDICATIONS USED TO TREAT 1326
4 MOM USED TO MAKE 1152
(further collocations 4 left and right)
1 MY 887
2 LIKE 176
3 RECIPE 37
4 GROWING 26
5 SOUP 25
6 KID 22
7 HOMEMADE 19
8 CHILDHOOD 18
9 CAKE 18
10 ONES 17
5 MATERIALS USED TO MAKE 1127
6 TERMS USED TO DESCRIBE 1122
7 THINGS USED TO BE 1096
(further collocations 4 left and right)
1 HOW 498
2 WAY 377
3 BACK 112
4 DONE 61
5 REMEMBER 32
6 REMINDER 22
7 STORIES 14
8 NOSTALGIC 12
9 TASTE 11
10 NOSTALGIA 9
8 TERM USED TO REFER 1087
9 MEDICINES USED TO TREAT 1048
10 DRUG USED TO TREAT 1001
11 MATERIAL USED TO MAKE 858
12 MEDICATION USED TO TREAT 843
13 WORDS USED TO DESCRIBE 808
14 WORD USED TO DESCRIBE 798
15 MEDICINE USED TO TREAT 554
16 PEOPLE USED TO SAY 518
17 MOTHER USED TO MAKE 511
18 CARD USED TO MAKE 470
19 GRANDMOTHER USED TO MAKE 456
20 GRANDMA USED TO MAKE 437
21 PEOPLE USED TO THINK 421
22 MOTHER USED TO SAY 410
23 LANGUAGE USED TO DESCRIBE 403
24 INGREDIENTS USED TO MAKE 393
25 CARD USED TO PURCHASE 382
26 DAD USED TO SAY 380
27 MATERIALS USED TO BUILD 377
28 LIFE USED TO BE 374
29 MATERIALS USED TO CREATE 367
30 METHOD USED TO DETERMINE 362
31 FORMULA USED TO CALCULATE 345
32 TECHNIQUES USED TO CREATE 343
33 FATHER USED TO SAY 342
34 PROCESS USED TO CREATE 341
35 CRITERIA USED TO DETERMINE 332
36 PROCESS USED TO MAKE 325
37 PEOPLE USED TO BE 320
38 PEOPLE USED TO DO 305
39 MATERIALS USED TO CONSTRUCT 289
40 PHRASE USED TO DESCRIBE 288
41 AREA USED TO BE 287
42 TERMINOLOGY USED TO DESCRIBE 286
43 CHEMICALS USED TO MAKE 269
44 TERM USED TO DEFINE 267
45 BUILDING USED TO BE 266
46 MOM USED TO SAY 255
47 ANTIBIOTIC USED TO TREAT 242
48 HOUSE USED TO BE 242
49 PLACE USED TO BE 238
50 SOFTWARE USED TO CREATE 234
51 DEVICE USED TO ACCESS 228
52 PEOPLE USED TO HAVE 225
53 ANTIBIOTICS USED TO TREAT 224
54 TOOLS USED TO CREATE 224
55 MATERIALS USED TO MANUFACTURE 222
56 PEOPLE USED TO LIVE 213
57 MOTHER USED TO TELL 212
58 GRANDMOTHER USED TO SAY 211
59 RATE USED TO CALCULATE 210
60 TERM USED TO DENOTE 208
61 FACTORS USED TO DETERMINE 207
62 MUM USED TO MAKE 207
63 DAD USED TO TAKE 206
64 METHOD USED TO CALCULATE 205
65 TECHNOLOGY USED TO CREATE 204
66 PEOPLE USED TO CALL 201
67 METHODS USED TO DETERMINE 196
68 TESTS USED TO DIAGNOSE 193
69 TECHNIQUE USED TO CREATE 191
70 PEOPLE USED TO USE 190
71 TERM USED TO INDICATE 190
72 FABRIC USED TO MAKE 189
73 PROCEDURE USED TO TREAT 186
74 PEOPLE USED TO GO 183
75 CRITERIA USED TO EVALUATE 181
76 MATERIALS USED TO PRODUCE 181
77 NUMBER USED TO IDENTIFY 181
78 DAD USED TO TELL 179
79 METHODS USED TO CREATE 179
80 TERM USED TO IDENTIFY 177
81 CARD USED TO PAY 176
82 FATHER USED TO TELL 174
83 PLASTIC USED TO MAKE 174
84 LANGUAGE USED TO CREATE 173
85 TECHNIQUES USED TO MAKE 173
86 TOOL USED TO CREATE 173
87 PEOPLE USED TO GET 172
88 PASSWORD USED TO ACCESS 171
89 PEOPLE USED TO COME 171
90 NAME USED TO DESCRIBE 169
91 METHOD USED TO CREATE 168
92 DATA USED TO CREATE 167
93 PEOPLE USED TO MAKE 165
94 GAME USED TO BE 162
95 ENERGY USED TO HEAT 160
96 TEST USED TO DETERMINE 160
97 KEY USED TO ENCRYPT 159
98 PROCESS USED TO PRODUCE 159
99 CRITERIA USED TO SELECT 158
100 FORMULA USED TO DETERMINE 158